Configuring a DHCP Server

S7700 V200R019C10 Configuration Guide - IP Service

This document describes the configurations of IP service, including IP address, ARP, DHCP, DNS, mDNS gateway, mDNS relay, UDP Helper, IP performance optimization, IPv6, DHCPv6, IPv6 DNS, IPv6 over IPv4 tunnel and IPv4 over IPv6 tunnel.

Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).

Enabling DHCP
Enabling the DHCP Server Function
(Optional) Configuring DHCP Data Restoration
(Optional) Configuring IP Address Conflict Detection
(Optional) Configuring a DHCP Server to Dynamically Allocate IP Addresses to BOOTP Clients
(Optional) Configuring the Abnormal Packet Detection Function
(Optional) Forcing a DHCP Server to Reply with a DHCP NAK Message
Configuring an Address Pool
Verifying the DHCP Server Configuration

Enabling DHCP

Context

Before enabling the DHCP server function, enable DHCP in the system view.

The dhcp enable command is the prerequisite for configuring DHCP-related functions, including DHCP relay, DHCP snooping, and DHCP server. These functions take effect only after the dhcp enable command is run. After the undo dhcp enable command is run, all DHCP-related configurations of the device are deleted. After DHCP is enabled again using the dhcp enable command, all DHCP-related configurations of the device are restored to the default configurations.
After DHCP is enabled, if STP is also enabled, address allocation may slow down. By default, STP is enabled. To disable STP, run the undo stp enable command.

Procedure

Enter the system view.
```
system-view
```
Enable DHCP.
```
dhcp enable
```
By default, DHCP is disabled.
(Optional) Enable dynamic route limiting on DHCP messages.
```
dhcp speed-limit auto
```
By default, dynamic rate limiting is disabled on DHCP messages.
(Optional) Enable the DHCP broadcast suppression function.
```
dhcp broadcast suppress enable
```
By default, the DHCP broadcast suppression function is disabled.

Enabling the DHCP Server Function

Context

Before a device can function as a DHCP server, you must enable DHCP. You can then enable the DHCP server function to operate based on an interface address pool or based on a global address pool.

Procedure

Enable the DHCP server function based on an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Configure an IP address for the interface.
```
ip address ip-address { mask | mask-length }
```
5. Enable the interface to use the interface address pool for providing the DHCP server function.
```
dhcp select interface
```
  By default, the DHCP server function using the interface address pool is disabled on an interface
  
  If the device functioning as the DHCP server provides the DHCP service for clients connected to multiple interfaces, repeat this step to enable the DHCP server function on all the interfaces.
Enable the DHCP server function based on a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Configure an IP address for the interface.
  1. Configure a primary IP address for the interface.
```
ip address ip-address { mask | mask-length }
```
  2. (Optional) Configure a secondary IP address for the interface.
```
ip address ip-address { mask | mask-length } sub
```
  The device can select a global address pool based on the primary and secondary IP addresses of an interface only in scenarios where the DHCP server and DHCP clients are on the same network segment.
  
  When clients connected to the interface configured with an IP address request IP addresses:
  - If the DHCP client and server are located in the same network segment (that is, no relay agent is deployed), the DHCP server selects the address pool based on the primary and secondary interface IP addresses. It preferentially allocates IP addresses from the address pool for the primary IP address. If IP addresses in this address pool are used up or this address pool is not configured, the DHCP server allocates IP addresses from the address pool for the secondary IP address.
  - If the DHCP server and client are located in different network segments (that is, a DHCP relay agent is used), the DHCP server selects the address pool in the same network segment as the IP address specified in the giaddr field of the received DHCP Request message.
5. Enable the interface to use the global address pool for providing the DHCP server function. (This step is optional if a DHCP relay agent is used.)
```
dhcp select global
```
  By default, an interface does not use the global address pool to provide the DHCP server function.
  
  After enabling the interface to use the global address pool for providing the DHCP server function, you need to configure the global IP address pool. For details, see Configuring an Address Pool.

(Optional) Configuring DHCP Data Restoration

Context

Automatically saving IP address allocation information allows the DHCP server to re-allocate the same configurations (such as IP address and lease time) to clients in the event that the server unexpectedly restarts.

After this function is enabled, the DHCP server stores lease information in lease.txt and conflicting IP addresses in conflict.txt (both data files are saved to the DHCP folder). New data files overwrite earlier data files.

The time displayed in the lease.txt and conflict.txt files is the UTC time rather than the system time, and you do not need to pay attention to time zone information.
To view information about the DHCP database, run the display dhcp server database command.
During the interval, if the device installed with MCUD, SRUHX1 or SRUHA1 restarts unexpectedly, DHCP data generated at the interval are lost. Users can only recover the last successfully saved DHCP data from storage device files.

Procedure

Enter the system view.
```
system-view
```
Enable the DHCP server to automatically save IP address allocation information.
```
dhcp server database enable
```
By default, the DHCP server does not automatically save IP address allocation information.
Specify the interval at which the DHCP server saves IP address allocation information.
```
dhcp server database write-delay interval
```
By default, IP address allocation information is saved every 7200 seconds in data files. The new data files overwrite the earlier data files.
Enable the DHCP server to recover IP address allocation information from the data files upon a restart.
```
dhcp server database recover
```
By default, the DHCP server is disabled from recovering IP address allocation information from the data files upon a restart.

(Optional) Configuring IP Address Conflict Detection

Context

IP address conflict detection uses ICMP to determine whether an IP address to be allocated conflicts with other IP addresses that are already allocated to clients. After this function is configured, a DHCP server sends an ICMP Echo Request message in which the source address is the IP address of the DHCP server and the destination address is the pre-allocated IP address for IP address conflict detection, before sending a DHCP Offer message to a client.

If the DHCP server does not receive any ICMP Echo Reply message within the detection period (Number of detections x Maximum wait time for each conflict detection), this IP address is not used by any client. The DHCP server allocates the IP address to the client by sending a DHCP Offer message.
If the DHCP server receives an ICMP Echo Reply message within the detection period (Number of detections x Maximum wait time for each conflict detection), this IP address is being used by a client. The DHCP server lists this IP address as a conflicting IP address and waits for the next DHCP Discover message to select another available IP address.

If the detection time is too long, clients may fail to obtain IP addresses. You are advised to set the detection time to less than 8 seconds.

Procedure

Enter the system view.
```
system-view
```
Specify the number of IP address conflict detections before IP address allocation.
```
dhcp server ping packet number
```
By default, the number of IP address conflict detections before IP address allocation is 2.
Specify the maximum wait time for each conflict detection.
dhcp server ping timeout milliseconds
By default, the maximum wait time for each conflict detection is 500 milliseconds.

(Optional) Configuring a DHCP Server to Dynamically Allocate IP Addresses to BOOTP Clients

Context

If you have BOOTP clients on your network and you want them to dynamically obtain IP addresses through DHCP, configure the DHCP server to service these clients.

Procedure

Enter the system view.
```
system-view
```
Enable the DHCP server to respond to BOOTP requests.
```
dhcp server bootp
```
By default, a DHCP server does not respond to BOOTP requests.
Enable the DHCP server to dynamically allocate IP addresses to BOOTP clients.
```
dhcp server bootp automatic
```
By default, a DHCP server does not dynamically allocate IP addresses to BOOTP clients.

(Optional) Configuring the Abnormal Packet Detection Function

Context

Devices from different vendors may use different DHCP implementation mechanisms. After detecting that the UDP header checksum or magic cookie field in a received DHCP packet fails the check, a device may not allow the DHCP packet to pass through and discards the packet. As a result, DHCP becomes unavailable. In this case, you can configure the device not to check the UDP header checksum or magic cookie field in received DHCP packets, so that DHCP packets with an incorrect UDP header checksum or incorrect value of the magic cookie field can still be properly forwarded.

According to the protocol, if the UDP header checksum is 0, the peer device does not verify the checksum in DHCP packets. If the peer device does not comply with the protocol, the peer device still verifies the checksum even if the UDP header checksum in DHCP packets sent by the local device is 0. In this case, you need to configure the local device to add the UDP header checksum to DHCP packets to be sent, so that the locally sourced DHCP packets can pass the checksum verification of the peer device.

A device, functioning as a DHCP server, DHCP relay agent, DHCP client, or DHCP snooping-enabled device, can be configured not to check the UDP header checksum or magic cookie field in received DHCP packets.
Only a device functioning as a DHCP server can be configured to add the UDP header checksum to DHCP packets to be sent.
After DHCP is enabled on a device, the device checks the IP header checksum and UDP header checksum in received DHCP packets by default. In addition, the function of checking the IP header checksum cannot be disabled.

Procedure

In the system view:
1. Run system-view
  The system view is displayed.
2. Configure the abnormal packet detection function.
  - Run undo dhcp anti-attack check magic-cookie
    
    The device is configured not to check the magic cookie field in received DHCP packets.
    
    By default, a device does not check the magic cookie field in received DHCP packets. Instead, the device directly forwards DHCP packets with an incorrect value of the magic cookie field.
  - Run undo dhcp anti-attack check udp-checksum
    
    The device is configured not to check the UDP header checksum in received DHCP packets.
    
    By default, a device checks the UDP header checksum in received DHCP packets and discards DHCP packets with an incorrect checksum.
  - Run dhcp udp-checksum enable
    The device is enabled to add the UDP header checksum in DHCP packets to be sent.
    
    By default, the UDP header checksum carried in DHCP packets sent by a device is 0, and the peer device does not verify the checksum.
In the VLAN view:
1. Run system-view
  The system view is displayed.
2. Run vlan vlan-id
  The VLAN view is displayed.
3. Configure the abnormal packet detection function.
  - Run undo dhcp anti-attack check magic-cookie
    
    The device is configured not to check the magic cookie field in received DHCP packets.
    
    By default, a device does not check the magic cookie field in received DHCP packets. Instead, the device directly forwards DHCP packets with an incorrect value of the magic cookie field.
  - Run undo dhcp anti-attack check udp-checksum
    
    The device is configured not to check the UDP header checksum in received DHCP packets.
    
    By default, a device checks the UDP header checksum in received DHCP packets and discards DHCP packets with an incorrect checksum.
In the interface view:
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. Configure the abnormal packet detection function.
  - Run undo dhcp anti-attack check magic-cookie
    
    The device is configured not to check the magic cookie field in received DHCP packets.
    
    By default, a device does not check the magic cookie field in received DHCP packets. Instead, the device directly forwards DHCP packets with an incorrect value of the magic cookie field.
  - Run undo dhcp anti-attack check udp-checksum
    
    The device is configured not to check the UDP header checksum in received DHCP packets.
    
    By default, a device checks the UDP header checksum in received DHCP packets and discards DHCP packets with an incorrect checksum.

(Optional) Forcing a DHCP Server to Reply with a DHCP NAK Message

Context

When a DHCP client goes online in two steps, the IP address requested by the DHCP client is in the IP address pool, but no lease record of the DHCP client is found in the address pool. For example, after obtaining an IP address from another DHCP server, a wireless user roams to the current DHCP server and the original IP address is in the address pool of the current DHCP server. Alternatively, the address pool is reset and the original user needs to go online again. In this case, when receiving a DHCP Request message from the DHCP client, the DHCP server keeps silent and does not reply the DHCP client with a DHCP NAK message. The DHCP client can apply for an IP address to go online again in four steps only after the two steps for the client to go online time out. As a result, the DHCP client is slow in obtaining an IP address. To force the DHCP server to reply with a DHCP NAK message, you can run the dhcp server force response command, so that the DHCP client can quickly enter the four-step process for going online and apply for an IP address again.

Procedure

Enter the system view.
```
system-view
```
Force the DHCP server to reply with a DHCP NAK message.
```
dhcp server force response
```
By default, a DHCP server is not forced to reply with a DHCP NAK message.

Configuring an Address Pool

Creating an Address Pool

Context

Create an interface address pool for IP address allocation to clients on the same network segment as the DHCP server's interface, or create a global address pool for IP address allocation to all clients connected to the DHCP server.

After an address pool is created, the following IP addresses on the network segment cannot be automatically assigned:

Network address (with host bits of all 0s)
Broadcast address (with host bits of all 1s)
Gateway address for DHCP clients (configured in (Optional) Configuring a Gateway Address for Clients)

Procedure

Create an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Configure an IP address for the interface.
```
ip address ip-address { mask | mask-length }
```
  The IP address segment of the interface is the interface address pool. The interface address mask cannot be set to 31; otherwise, the interface address pool may fail to be configured.
Create a global address pool.
1. Enter the system view.
```
system-view 
```
2. Create a global address pool and enter the global address pool view.
```
ip pool ip-pool-name
```
  By default, no global address pool is created on the device.
  
  The parameter ip-pool-name uniquely specifies the name of an address pool. For example, create a global address pool named global_f1 for employees on the first floor as follows:
  
  [HUAWEI] ip pool global_f1
3. Specify the range of IP addresses to be dynamically allocated from the address pool.
```
network ip-address [ mask { mask | mask-length } ]
```
  By default, the range of IP addresses that can be allocated dynamically to clients is not specified.
  
  An address pool can be configured with only one IP address segment. The IP address range is determined by the mask length.
  
  When specifying the IP address range, ensure that IP addresses within the range are on the same network segment as the interface IP address of the DHCP server or DHCP relay agent to avoid incorrect IP address allocation.
  
  When configuring an address pool, ensure that IP addresses on the network address segment must be class A, B, or C IP addresses, and the mask cannot be set to 0, 1, 31, or 32.
4. (Optional) Configure a VPN instance for the address pool.
```
vpn-instance vpn-instance-name
```
  By default, no VPN instance is configured for an address pool.
  
  In most cases, IP addresses in an address pool are allocated to clients on only one network segment to prevent IP address conflicts. In a BGP/MPLS IP VPN scenario, different VPNs use IP addresses on the same network segment. If clients in different VPNs apply to the same DHCP server for IP addresses, perform this step to use the same address pool to allocate IP addresses on the same network segment to the clients.

(Optional) Configuring the Range of IP Addresses in an Address Pool

Context

This configuration allows you to determine the scope of IP addresses that a DHCP server can allocate.

Procedure

Configure a range in an interface address pool:
1. Enter the system view.
```
system-view 
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify the range of IP addresses that the DHCP server can allocate.
```
dhcp server ip-range start-ip-address end-ip-address
```
5. Specify the subnet mask for the range of IP addresses.
```
dhcp server mask { mask | mask-length }
```
Global address pool:
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify the IP address segment of the global address pool.
```
section section-id start-address [ end-address ]
```
  An IP address pool can contain one or more IP address segments that cannot overlap with each other.
  Note the following points when specifying IP address segment of the global address pool:
  - If you run the network (IP address pool view) first, ensure that the address segment specified in the section (IP address pool view) command is included in the address range specified in the network (IP address pool view) command.
  - If you run the section (IP address pool view) first, ensure that the address segment specified in the network (IP address pool view) command includes the address range specified in the section (IP address pool view) command.

(Optional) Excluding IP Addresses from an Address Pool

Context

To prevent a DHCP server from allocating specific IP addresses, exclude these IP addresses from the address pool.

You do not need to exclude the gateway address configured using the gateway-list or dhcp server gateway-list command from being automatically allocated. The device automatically adds the gateway address into the list of IP addresses that cannot be automatically allocated.

You do not need to exclude the IP address of a server's interface connecting to a client from being automatically allocated. The device automatically sets the interface IP address to the Conflict status during address allocation.

Procedure

Exclude IP addresses from an interface address pool.
1. Enter the system view.
```
system-view 
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify the range of IP addresses to exclude from the address pool.
```
dhcp server excluded-ip-address start-ip-address [ end-ip-address ]
```
  By default, all IP addresses are automatically allocated from the address pool.
  
  To set multiple IP address ranges that cannot be automatically allocated from the address pool, run this command multiple times.
  
  For example, to exclude 192.168.1.10 from the range of IP addresses that can be automatically allocated, run:
  
  [HUAWEI-Vlanif100] dhcp server excluded-ip-address 192.168.1.10
Exclude IP addresses from a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify the range of IP addresses to exclude from the address pool.
```
excluded-ip-address start-ip-address [ end-ip-address ]
```
  By default, all IP addresses are automatically allocated from the address pool.
  
  To set multiple IP address ranges that cannot be automatically allocated from the address pool, run this command multiple times.
  
  For example, to exclude 192.168.1.10 from the range of IP addresses that can be automatically allocated, run:
  
  [HUAWEI-ip-pool-global_f1] excluded-ip-address 192.168.1.10

Follow-up Procedure

If you want to add more ranges of IP addresses that cannot be automatically allocated from the address pool, run the dhcp server excluded-ip-address or excluded-ip-address command for multiple times. If you want to delete some configured ranges of IP addresses that cannot be automatically allocated from the address pool, run the undo dhcp server excluded-ip-address or undo excluded-ip-address command.

The following uses the global address pool global1 as an example. You can run the following commands to exclude IP addresses in the range from 10.10.10.10 to 10.10.10.30 from the global address pool.

<HUAWEI> system-view
[HUAWEI] ip pool global1
[HUAWEI-ip-pool-global1] network 10.10.10.0 mask 24
[HUAWEI-ip-pool-global1] excluded-ip-address 10.10.10.10 10.10.10.30
[HUAWEI-ip-pool-global1] quit

If you want to exclude IP addresses in the range from 10.10.10.10 to 10.10.10.40 from the global address pool, run the following commands:
```
[HUAWEI] ip pool global1
[HUAWEI-ip-pool-global1] excluded-ip-address 10.10.10.10 10.10.10.40
[HUAWEI-ip-pool-global1] quit
```

If you want to exclude IP addresses only in the range from 10.10.10.15 to 10.10.10.20 from the global address pool, run the following commands:

[HUAWEI] ip pool global1
[HUAWEI-ip-pool-global1] undo excluded-ip-address 10.10.10.10 10.10.10.14
[HUAWEI-ip-pool-global1] undo excluded-ip-address 10.10.10.21 10.10.10.30
[HUAWEI-ip-pool-global1] quit

(Optional) Configuring Fixed IP Addresses in an Address Pool

Context

A DHCP server leases IP addresses to clients. When the lease expires, the clients must apply for new IP addresses. To ensure stability, certain clients require fixed IP addresses. In this case, configure the DHCP server to allocate fixed IP addresses to these clients. The MAC addresses of these clients are then bound to fixed IP addresses. When such a client applies to the DHCP server for an IP address, the DHCP server searches the binding entries for the MAC address of the client and allocates the matched IP address to the client. DHCP static allocation prevents manual configuration errors and facilitates unified management.

Ensure that the bound IP address is not configured as the IP address that cannot be allocated.
IP addresses that are used can also be statically bound to MAC addresses or unbound from MAC addresses. When an IP address is statically bound to a MAC address, ensure that the MAC address to be bound is the same as the MAC address of the user who actually uses the IP address.
After an IP address is bound to a MAC address, the IP address does not expire. After an automatically allocated IP address is statically bound to a MAC address, the lease time of the IP address becomes unlimited. After the static binding between the IP address and the MAC address is deleted, the lease time of the IP address becomes the same as that configured in the address pool.

The binding of IP addresses and MAC addresses is used in DHCP static allocation, IPSG (for details on how to configure IPSG, see IP source guard in the S7700 V200R019C10 Configuration Guide - Security), and static ARP. Table 3-7 lists different usage scenarios and implementations of these functions.

Table 3-7 Differences between DHCP static allocation, IPSG, and static ARP

Function	Scenario	Implementation
DHCP static allocation	Some clients (such as servers and PCs) require fixed IP addresses from a DHCP server.	The MAC addresses of these clients are bound to fixed IP addresses. When such a client applies to the DHCP server for an IP address, the DHCP server searches the binding entries for the MAC address of the client and allocates the matched IP address to the client.
IPSG	Attacks including IP address spoofing and ARP spoofing need to be prevented: IP address spoofing: An attacker uses a forged IP address and its own MAC address to obtain rights of the attacked device and intercept packets destined for the attacked device. ARP spoofing: An attacker sends ARP packets using a forged MAC address to intercept packets destined for the attacked device or using the MAC address of the gateway to intercept all packets destined for the gateway.	The mapping between IP addresses and MAC addresses is set up on a device. When receiving an ARP Request packet, the device searches for the mapped MAC address based on the source IP address of the packet and compares the mapped MAC address with the source MAC address in the packet header. If the two MAC addresses are different from each other, the device considers the packet invalid and discards it.
Static ARP	The mapping between IP addresses and MAC addresses is manually configured in the following scenarios: Packets whose destination IP addresses are not on the local network segment need to be forwarded by a gateway on the local network segment. Destination IP addresses of invalid packets need to be bound to a nonexistent MAC address to filter them out. Critical devices need to forward packet securely and be protected against attacks, such as ARP flooding. In this situation, static ARP entries can be configured to bind MAC addresses to specific IP addresses. Network attackers cannot modify the mapping between the IP and MAC addresses, which ensures communication between the two devices.	The mapping between IP addresses and MAC addresses is set up on a device. When receiving an ARP Request packet, the device searches for the MAC address mapped to the IP address in the packet and responds with an ARP Reply packet. Static ARP entries are manually configured and maintained. These entries are neither aged nor overwritten by dynamic ARP entries, and therefore improve communication security.

Function

Scenario

Implementation

DHCP static allocation

Some clients (such as servers and PCs) require fixed IP addresses from a DHCP server.

The MAC addresses of these clients are bound to fixed IP addresses. When such a client applies to the DHCP server for an IP address, the DHCP server searches the binding entries for the MAC address of the client and allocates the matched IP address to the client.

IPSG

Attacks including IP address spoofing and ARP spoofing need to be prevented:

IP address spoofing: An attacker uses a forged IP address and its own MAC address to obtain rights of the attacked device and intercept packets destined for the attacked device.
ARP spoofing: An attacker sends ARP packets using a forged MAC address to intercept packets destined for the attacked device or using the MAC address of the gateway to intercept all packets destined for the gateway.

The mapping between IP addresses and MAC addresses is set up on a device. When receiving an ARP Request packet, the device searches for the mapped MAC address based on the source IP address of the packet and compares the mapped MAC address with the source MAC address in the packet header. If the two MAC addresses are different from each other, the device considers the packet invalid and discards it.

Static ARP

The mapping between IP addresses and MAC addresses is manually configured in the following scenarios:

Packets whose destination IP addresses are not on the local network segment need to be forwarded by a gateway on the local network segment.
Destination IP addresses of invalid packets need to be bound to a nonexistent MAC address to filter them out.
Critical devices need to forward packet securely and be protected against attacks, such as ARP flooding. In this situation, static ARP entries can be configured to bind MAC addresses to specific IP addresses. Network attackers cannot modify the mapping between the IP and MAC addresses, which ensures communication between the two devices.

The mapping between IP addresses and MAC addresses is set up on a device. When receiving an ARP Request packet, the device searches for the MAC address mapped to the IP address in the packet and responds with an ARP Reply packet.

Static ARP entries are manually configured and maintained. These entries are neither aged nor overwritten by dynamic ARP entries, and therefore improve communication security.

Procedure

Configure a fixed IP address in an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Bind an IP address to a MAC address so that the DHCP server allocates this IP address to only the device with this MAC address.
```
dhcp server static-bind ip-address ip-address mac-address mac-address [ description description ]
```
  By default, a DHCP server does not allocate fixed IP addresses to specified clients.
Configure a fixed IP address in a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Bind an IP address to a MAC address so that the DHCP server allocates this IP address to only the device with this MAC address.
```
static-bind ip-address ip-address mac-address mac-address [ option-template template-name | description description ]
```
  By default, a DHCP server does not allocate fixed IP addresses to specified clients.

(Optional) Configuring an Address Lease Time

Context

The default lease time in an address pool is 1 day. An administrator can change an address lease time based on network requirements. IP addresses in the same address pool use the same lease time, and different address pools can have different address leases specified. After the lease of an address pool is changed, newly allocated IP addresses use the new lease. The IP addresses that have been allocated before the lease is changed still use the old lease before the old lease is updated and use the new lease after the old lease is updated.

BOOTP clients do not support Option 51 (the IP address lease option). The lease of IP addresses allocated to BOOTP clients is unlimited, and these IP addresses will not be reclaimed by DHCP servers.

The IP addresses statically allocated to clients are always valid, without being limited by address lease time.

Procedure

Configure a lease time based on an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify an IP address lease time.
```
dhcp server lease { day day [ hour hour [ minute minute ] ] | unlimited }
```
  By default, the IP address lease is 1 day.
Configure a lease time based on a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify an IP address lease time.
```
lease { day day [ hour hour [ minute minute ] ] | unlimited }
```
  By default, the IP address lease is 1 day.

Verifying the Configuration

Run the display ip pool command to view information about the IP address lease. The values of the lease and left fields in the command output indicate the configured lease time and remaining lease time, respectively.

(Optional) Configuring Automatic Reclaim of Conflicting IP Addresses in an Address Pool

Context

When a DHCP server allocates IP addresses to clients, IP address conflict may occur because IP addresses of some hosts have been manually configured. In this case, the DHCP server considers these IP addresses as conflicting IP addresses, and allocates available IP addresses from the conflicting IP addresses to clients only after available IP addresses in the address pool are used up. To reclaim conflicting IP addresses promptly, the administrator can enable automatic reclaim and specify the reclaim interval.

Procedure

Interface address pool:
1. Run system-view
  The system view is displayed.
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Run dhcp server conflict auto-recycle interval day day [ hour hour [ minute minute ] ]
  Automatic reclaim of conflicting IP addresses in the interface address pool is enabled and the interval for the automatic reclaim is configured.
  
  By default, automatic reclaim of conflicting IP addresses in the interface address pool is disabled.
Global address pool:
1. Run system-view
  The system view is displayed.
2. Run ip pool ip-pool-name
  The global address pool view is displayed.
3. Run conflict auto-recycle interval day day [ hour hour [ minute minute ] ]
  Automatic reclaim of conflicting IP addresses in the global address pool is enabled and the interval for the automatic reclaim is configured.
  
  By default, automatic reclaim of conflicting IP addresses in the global address pool is disabled.

(Optional) Configuring the Alarm Function for IP Address Exhaustion

Context

To receive notifications about IP address exhaustion, configure the DHCP to generate alarms for IP address exhaustion.

Procedure

Configure the alarm function in an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify the percentage of alarms indicating the exhaustion of IP addresses and the percentage of clear alarms.
```
dhcp server alarm ip-used percentage alarm-resume-percentage alarm-percentage
```
  By default, the percentage of the alarms is 100%, and the percentage of the clear alarms is 50%.
Configure the alarm function in a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify the percentage of alarms indicating the exhaustion of IP addresses and the percentage of clear alarms.
  alarm ip-used percentage alarm-resume-percentage alarm-percentage
  By default, the percentage of the alarms is 100%, and the percentage of the clear alarms is 50%.

(Optional) Configuring the Logging Function for IP Address Allocation

Context

Configuring the DHCP server to log IP address allocation provides you with records that may facilitate maintenance and diagnostics.

With this logging function enabled, if a large number of DHCP clients request IP addresses from the DHCP server, the server frequently records logs. The server performance may therefore be affected.
IP address allocation logs are recorded in the AM module. To view log information, the information center must be enabled. In addition, default settings for log output vary depending on various factors including the log level and output direction. For details, see Information Center Configuration in the CLI-based Configuration - Device Management Configuration Guide.
For example, the level of logs indicating that an IP address is successfully allocated, an IP address is successfully renewed, and an IP address is successfully released is informational, and these logs are not recorded in the log buffer by default. You can run the info-center source AM channel 4 log level informational command to change the level of the logs to be recorded in the log buffer. You can then run the display logbuffer command to check the preceding logs.

Procedure

Configure the logging function in an interface address pool.
1. Enter the system view.
```
system-view 
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Enable the DHCP server to record IP address allocation logs.
```
dhcp server logging [ allocation-fail | allocation-success | release | renew-fail | renew-success | detect-conflict | recycle-conflict ] ^*
```
  By default, the logging function is disabled.
Configure the logging function in a global address pool.
1. Enter the system view.
```
system-view 
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Enable the DHCP server to record IP address allocation logs.
```
logging [ allocation-fail | allocation-success | release | renew-fail | renew-success | detect-conflict | recycle-conflict ] ^*
```
  By default, the logging function is disabled.

(Optional) Configuring a Gateway Address for Clients

Context

If a gateway address for clients is configured on the DHCP server, clients obtain the gateway address from the DHCP server and automatically generate a default route to the gateway address. Then the clients can access the hosts on other network segments. If the DHCP server is configured with Option 121 to allocate classless static routes to clients, the clients generate routes based on only the static routes and does not generate a default route to the gateway address. To load balance traffic and improve network reliability, configure multiple gateway addresses. A maximum of eight gateway addresses can be configured for each address pool.

In the scenario where both VRRP and DHCP are configured, if a VRRP group functions as the DHCP server, configure the gateway address of clients as the virtual IP address of the VRRP group.

If the DHCP server and clients are on the same network segment and the DHCP server functions as the gateway of clients, you do not need to configure a gateway address for clients.

Procedure

Configure a gateway address in the interface address pool view.
1. Enter the system view.
```
system-view 
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify a gateway address that the DHCP server sends to clients.
```
dhcp server gateway-list ip-address &<1-8>
```
  By default, no gateway address is configured.
Configure a gateway address in the global address pool view.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify a gateway address that the DHCP server sends to clients.
```
gateway-list ip-address &<1-8>
```
  By default, no egress gateway address is configured.
Configure a gateway address in the DHCP Option template view.
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. Specify a gateway address that the DHCP server sends to clients.
```
gateway-list ip-address &<1-8>
```
  By default, no egress gateway address is configured.
  
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
4. (Optional) Return to the system view.
```
quit
```
5. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
6. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

(Optional) Configuring a Configuration File for a DHCP Client

Context

DHCP can be used to deliver configuration files to clients that require them for startup. You can save the configuration files on the DHCP server or specify the IP address of a dedicated file server. When a configuration file exists on a dedicated file server, the DHCP server needs to specify the IP address of the file server for clients. You can also specify an IP address for the file server by configuring user-defined options for clients.

If the startup configuration file is saved on a file server, the route between the DHCP client and file server must be reachable.

Procedure

Configure a configuration file based on an interface address pool.
1. Enter the system view.
```
system-view 
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify the name of the configuration file.
```
dhcp server bootfile bootfile
```
  By default, the name is not configured.
5. Specify the name of the server that hosts the configuration file.
```
dhcp server sname sname
```
  By default, the name of the server is not configured.
6. (Optional) Specify the IP address of the file server that hosts the configuration file.
```
dhcp server next-server ip-address
```
  By default, the file server IP address is not configured.
Configure a configuration file based on a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify the name of the configuration file.
```
bootfile bootfile
```
  By default, the name is not configured.
4. Specify the name of the server that hosts the configuration file.
```
sname sname
```
  By default, the name of the server is not configured.
5. Specify the IP address of the file server that hosts the configuration file.
```
next-server ip-address 
```
  By default, the file server IP address is not configured.
In the DHCP Option template view:
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. Specify the name of the configuration file.
```
bootfile bootfile
```
  By default, the name of the startup configuration file for DHCP clients is not configured.
4. Specify the name of the server that hosts the configuration file.
```
sname sname
```
  By default, the name of the server from which a DHCP client obtains the startup configuration file is not configured.
5. (Optional) Specify the name of the server that hosts the configuration file.
```
next-server ip-address
```
  By default, the server IP address is not configured for the client after the client automatically obtains the IP address.
  
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
6. (Optional) Return to the system view.
```
quit
```
7. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
8. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

(Optional) Configuring User-defined Options

Context

Vendors can define DHCP options. The device can function as a DHCP server to allocate vendor-defined network parameters to clients. When the device functions as a DHCP server, it can allocate network parameters using either of the following methods:

Based on the options in DHCP Discovery messages
The device inserts an option configured using the dhcp server option (based on an interface address pool) or option (based on a global address pool) command into DHCP Reply messages to be sent to a client only when the client requests this option.
By forcibly appending the option field
The device inserts an option configured using the dhcp server force insert option (based on an interface address pool) or force insert option (based on a global address pool) command into DHCP Reply messages to be sent to a client regardless of whether the client requests this option.

Procedure

Configure user-defined options based on an interface address pool.

Enter the system view.
```
system-view
```
(Optional) Enable the DHCP server to trust Option 82.
```
dhcp server trust option82
```
By default, the device is enabled to trust Option 82.
(Optional) Enable the DHCP server to check and discard DHCP messages with duplicate options.
```
 dhcp anti-attack check duplicate option [ option-start [ to option-end ] ] &<1-254>
```
By default, a device is disabled from checking and discarding DHCP messages with duplicate options.

Enter the interface or sub-interface view.

interface interface-type interface-number[.subinterface-number ]

(Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.

By default, an Ethernet interface works in Layer 2 mode.
(Optional) Force the DHCP server to insert a specified option field into DHCP Reply messages.
```
dhcp server force insert option code &<1-254>
```
By default, the DHCP server does not forcibly insert a specified option field into DHCP Reply messages.

After this function is configured, the device inserts an option field into DHCP Reply messages to be sent to clients regardless of whether the clients request this option.

Configure user-defined options.

dhcp server option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }

By default, no user-defined option is configured.

If an option carries a password, the option code in ascii or hex type is insecure. Therefore, you are advised to set the option code type to cipher. For security purposes, use a password that is at least six characters long and contains at least two types of the following: lowercase letters, uppercase letters, digits, and special characters.

After an option is configured, the device inserts the option into DHCP Reply messages to be sent to clients only when the clients request this option.

Not all options can be configured using the preceding command. The following table lists the options and their commands.

Table 3-8 Commands for configuring options

Option	Configuration Command	Description
Option1	mask-length in the ip address ip-address { mask \| mask-length } command	Subnet mask
Option3	ip-address in the ip address ip-address { mask \| mask-length } command	Gateway address
Option6	dhcp server dns-list ip-address &<1-8>	DNS server IP address
Option15	dhcp server domain-name (interface view) domain-name	Domain name
Option44	dhcp server nbns-list ip-address &<1-8>	NetBIOS server IP address
Option46	dhcp server netbios-type { b-node \| h-node \| m-node \| p-node }	NetBIOS node type
Option50	N/A	Requested IP address
Option51	dhcp server lease { day day [ hour hour [ minute minute ] ] \| unlimited }	IP address lease
Option52	N/A	Additional option
Option53	N/A	DHCP message type
Option54	N/A	Server identifier
Option55	N/A	Parameter request list
Option57	N/A	Maximum length of a DHCP message
Option58	N/A	Lease renewal time (T1), which is 50% of the lease time
Option59	N/A	Lease renewal time (T2), which is 87.5% of the lease time
Option61	N/A	Client identifier
Option82	N/A	Relay agent information
Option120	dhcp server sip-server { ip-address ip-address &<1-2> \| list domain-name &<1-2> }	SIP server IP address
Option121	dhcp server option121 ip-address { ip-address mask-length gateway-address } &<1-8>	A group of classless routes
Option184	dhcp server option184 { as-ip ip-address \| fail-over ip-address dialer-string \| ncp-ip ip-address \| voice-vlan vlan-id }	Voice parameters

Configure user-defined options based on a global address pool.

In the global address pool view:

Enter the system view.
```
system-view
```
(Optional) Enable the DHCP server to trust Option 82.
```
dhcp server trust option82
```
By default, the device is enabled to trust Option 82.
Enter the global address pool view.
```
ip pool ip-pool-name
```
(Optional) Force the DHCP server to insert a specified option field into DHCP Reply messages.
```
force insert option code &<1-254>
```
By default, the DHCP server does not forcibly insert a specified option field into DHCP Reply messages.

Configure user-defined options.

option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }

By default, no user-defined option is configured.

Not all options can be configured using the preceding command. The following table lists the options and their commands.

Table 3-9 Commands for configuring options

Option	Configuration Command	Description
Option1	mask-length in the network (IP address pool view) ip-address [ mask { mask \| mask-length } ]	Subnet mask
Option3	gateway-list ip-address &<1-8>	Gateway address
Option6	dns-list ip-address &<1-8>	DNS server IP address
Option15	domain-name domain-name	Domain name suffix
Option44	nbns-list ip-address &<1-8>	NetBIOS server IP address
Option46	netbios-type { b-node \| h-node \| m-node \| p-node }	NetBIOS node type
Option50	N/A	Requested IP address
Option51	lease { day day [ hour hour [ minute minute ] ] \| unlimited }	IP address lease
Option52	N/A	Additional option
Option53	N/A	DHCP message type
Option54	N/A	Server identifier
Option55	N/A	Parameter request list
Option57	N/A	Maximum length of a DHCP message
Option58	N/A	Lease renewal time (T1), which is 50% of the lease time
Option59	N/A	Lease renewal time (T2), which is 87.5% of the lease time
Option61	N/A	Client identifier
Option82	N/A	Relay agent information
Option120	sip-server { ip-address ip-address &<1-2> \| list domain-name &<1-2> }	SIP server IP address
Option121	option121 ip-address { ip-address mask-length gateway-address } &<1-8>	A group of classless routes
Option184	option184 { as-ip ip-address \| fail-over ip-address dialer-string \| ncp-ip ip-address \| voice-vlan vlan-id }	Voice parameters

In the DHCP Option template view:
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. (Optional) Force the DHCP server to insert a specified option field into DHCP Reply messages.
```
force insert option code &<1-254>
```
  By default, the DHCP server does not forcibly insert a specified option field into DHCP Reply messages.
4. Configure user-defined options.
```
option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }
```
  By default, no user-defined option is configured.
  
  If an option carries a password, the option code in ascii or hex type is insecure. Therefore, you are advised to set the option code type to cipher. For security purposes, use a password that is at least six characters long and contains at least two types of the following: lowercase letters, uppercase letters, digits, and special characters.
  
  Not all options can be configured using the preceding command. See Table 3-9 for the list of options and their commands.
5. Configure a classless static route to be allocated to clients.
```
option121 ip-address { ip-address mask-length gateway-address } &<1-8>
```
  By default, no classless static route to be allocated to DHCP clients is configured.
6. Configure Option 184.
```
option184 { as-ip ip-address | fail-over ip-address dialer-string | ncp-ip ip-address | voice-vlan vlan-id }
```
  By default, the Option 184 field is not configured.
  
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
7. (Optional) Return to the system view.
```
quit
```
8. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
9. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

(Optional) Configuring DNS Configurations Allocated by a DHCP Server

Context

If DHCP clients on your network use DNS and you want them to receive DNS configurations through DHCP, configure the DHCP server to provide DNS configurations.

Procedure

Based on an interface address pool
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Configure the IP address of a DNS server for DHCP clients.
```
dhcp server dns-list { ip-address &<1-8> | unnumbered interface interface-type interface-number }
```
  By default, no DNS server IP address is configured in an address pool.
  
  Each address pool can be configured with a maximum of eight DNS server IP addresses.
5. Configure a domain name that is allocated to DHCP clients.
```
dhcp server domain-name domain-name
```
  By default, no domain name is allocated.
Based on a global address pool in the global address pool view
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Configure the IP address of a DNS server.
```
dns-list ip-address &<1-8>
```
  By default, no DNS server IP address is configured in an address pool.
  
  Each address pool can be configured with a maximum of eight DNS server IP addresses.
4. Configure a domain name that is allocated to DHCP clients.
```
domain-name domain-name
```
  By default, no DNS domain name suffix is configured.
In the DHCP Option template view
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. Configure the DNS server IP address and DNS domain name suffix to be allocated to DHCP clients.
  - Configure the DNS server IP address to be allocated to DHCP clients.
```
dns-list ip-address &<1-8>
```
    By default, no DNS server IP address is configured.
    
    Each address pool can be configured with a maximum of eight DNS server IP addresses.
  - Configure the DNS domain name suffix to be allocated to DHCP clients.
```
domain-name domain-name
```
    By default, no DNS domain name suffix is configured.
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
4. (Optional) Return to the system view.
```
quit
```
5. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
6. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

(Optional) Configuring NetBIOS Configurations Allocated by a DHCP Server

Context

If DHCP clients on your network use NetBIOS and you want them to receive NetBIOS configurations through DHCP, configure the DHCP server to provide NetBIOS configurations.

Procedure

Based on an interface address pool
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Configure the NetBIOS server IP address and NetBIOS node type to be allocated to DHCP clients.
  - Configure the NetBIOS server IP address to be allocated to DHCP clients.
```
dhcp server nbns-list ip-address &<1-8>
```
    By default, no NetBIOS server IP address is configured in an address pool.
    
    Each address pool can be configured with a maximum of eight NetBIOS server IP addresses.
  - Configure a NetBIOS node type to be allocated to DHCP clients.
```
dhcp server netbios-type { b-node | h-node | m-node | p-node }
```
    By default, no NetBIOS node type is configured for DHCP clients.
Based on a global address pool in the global address pool view
1. Enter the system view.
```
system-view 
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Configure the NetBIOS server IP address and NetBIOS node type to be allocated to DHCP clients.
  - Configure the NetBIOS server IP address to be allocated to DHCP clients.
```
nbns-list ip-address &<1-8>
```
    By default, no NetBIOS server IP address is configured in an address pool.
    
    Each address pool can be configured with a maximum of eight NetBIOS server IP addresses.
  - Configure a NetBIOS node type to be allocated to DHCP clients.
```
netbios-type { b-node | h-node | m-node | p-node }
```
    By default, no NetBIOS node type is configured.
In the DHCP Option template view
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. Configure the NetBIOS server IP address and NetBIOS node type to be allocated to DHCP clients.
  - Configure the NetBIOS server IP address to be allocated to DHCP clients.
```
nbns-list ip-address &<1-8>
```
    By default, no NetBIOS server IP address is configured.
    
    Each address pool can be configured with a maximum of eight NetBIOS server IP addresses.
  - Configure a NetBIOS node type to be allocated to DHCP clients.
```
netbios-type { b-node | h-node | m-node | p-node }
```
    By default, no NetBIOS node type is configured.
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
4. (Optional) Return to the system view.
```
quit
```
5. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
6. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

(Optional) Configuring a SIP Server Address to Be Allocated by the DHCP Server

Context

When you configure a SIP server IP address in an address pool, the DHCP server specifies the SIP server IP address when allocating IP addresses to DHCP clients.

Procedure

Configure a SIP server address in an interface address pool.
1. Enter the system view.
```
system-view
```
2. Enter the interface or sub-interface view.
```
interface interface-type interface-number[.subinterface-number ]
```
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
4. Specify the IP address of a SIP server.
```
dhcp server sip-server { ip-address ip-address &<1-2> | list domain-name &<1-2> }
```
  By default, no SIP server IP address is configured.
Configure a SIP server address in a global address pool.
1. Enter the system view.
```
system-view
```
2. Enter the global address pool view.
```
ip pool ip-pool-name
```
3. Specify the IP address of a SIP server.
```
sip-server { ip-address ip-address &<1-2> | list domain-name &<1-2> }
```
  By default, no SIP server IP address is configured.
Configure a SIP server address in the DHCP Option template view.
1. Enter the system view.
```
system-view
```
2. Create a DHCP Option template and enter the DHCP Option template view.
```
dhcp option template template-name
```
  By default, no DHCP Option template is created.
  
  To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
  
  To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
3. Configure the SIP server IP address to be allocated to DHCP clients.
```
sip-server { ip-address ip-address &<1-2> | list domain-name &<1-2> }
```
  By default, no SIP server IP address is configured in the DHCP Option template view.
  
  If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
4. (Optional) Return to the system view.
```
quit
```
5. (Optional) Enter the global address pool view.
```
ip pool ip-pool-name
```
6. (Optional) Bind a DHCP Option template to static clients.
```
static-bind ip-address ip-address mac-address mac-address option-template template-name
```

Verifying the DHCP Server Configuration

Procedure

Check IP address allocation information in address pools using the following commands:
- Interface address pool:
  
  display ip pool [ interface interface-pool-name [ start-ip-address [ end-ip-address ] | all | conflict | expired | used ] ]
- Global address pool:
  
  display ip pool [ name ip-pool-name [ start-ip-address [ end-ip-address ] | all | conflict | expired | used [ user-type { dhcp | pppoe | l2tp | ipsec | ssl-vpn | ppp } ] ] ]
Run the display dhcp server database command to view the path for storing the DHCP database.
Run the display dhcp option template [ name template-name ] command to view the configuration of a DHCP Option template.
Run the display dhcp server configuration command to check configurations about the DHCP server.

Enabling DHCP
Enabling the DHCP Server Function
(Optional) Configuring DHCP Data Restoration
(Optional) Configuring IP Address Conflict Detection
(Optional) Configuring a DHCP Server to Dynamically Allocate IP Addresses to BOOTP Clients
(Optional) Configuring the Abnormal Packet Detection Function
(Optional) Forcing a DHCP Server to Reply with a DHCP NAK Message
Configuring an Address Pool
Verifying the DHCP Server Configuration

Translation

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Updated: 2022-05-24

Document ID: EDOC1100126851

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Corporate

This document describes the configurations of IP service, including IP address, ARP, DHCP, DNS, mDNS gateway, mDNS relay, UDP Helper, IP performance optimization, IPv6, DHCPv6, IPv6 DNS, IPv6 over IPv4 tunnel and IPv4 over IPv6 tunnel.

Enabling DHCP

Context

Procedure

Enabling the DHCP Server Function

Context

Procedure

(Optional) Configuring DHCP Data Restoration

Context

Procedure

(Optional) Configuring IP Address Conflict Detection

Context

Procedure

(Optional) Configuring a DHCP Server to Dynamically Allocate IP Addresses to BOOTP Clients

Context

Procedure

(Optional) Configuring the Abnormal Packet Detection Function

Context

Procedure

(Optional) Forcing a DHCP Server to Reply with a DHCP NAK Message

Context

Procedure

Configuring an Address Pool

Creating an Address Pool

Context

Procedure

(Optional) Configuring the Range of IP Addresses in an Address Pool

Context

Procedure

(Optional) Excluding IP Addresses from an Address Pool

Context

Procedure

Follow-up Procedure

(Optional) Configuring Fixed IP Addresses in an Address Pool

Context

Procedure

(Optional) Configuring an Address Lease Time

Context

Procedure

Verifying the Configuration

(Optional) Configuring Automatic Reclaim of Conflicting IP Addresses in an Address Pool

Context

Procedure

(Optional) Configuring the Alarm Function for IP Address Exhaustion

Context

Procedure

(Optional) Configuring the Logging Function for IP Address Allocation

Context

Procedure

(Optional) Configuring a Gateway Address for Clients

Context

Procedure

(Optional) Configuring a Configuration File for a DHCP Client

Context

Procedure

(Optional) Configuring User-defined Options

Context

Procedure

(Optional) Configuring DNS Configurations Allocated by a DHCP Server

Context

Procedure

(Optional) Configuring NetBIOS Configurations Allocated by a DHCP Server

Context

Procedure

(Optional) Configuring a SIP Server Address to Be Allocated by the DHCP Server

Context

Procedure

Verifying the DHCP Server Configuration

Procedure

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