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Configuration Guide - IP Service

S7700 and S9700 V200R013C00

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.
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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).
Configuring a DHCP Server

Configuring a DHCP Server

Enabling DHCP

Context

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

NOTE:
  • 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

  1. Enter the system view.

    system-view

  2. Enable DHCP.

    dhcp enable

    By default, DHCP is disabled.

  3. (Optional) Enable dynamic route limiting on DHCP messages.

    dhcp speed-limit auto

    By default, dynamic rate limiting is disabled on DHCP messages.

  4. (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

      NOTE:

      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, 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.

(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.

NOTE:
  • 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 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

  1. Enter the system view.

    system-view

  2. 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.

  3. 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.

  4. 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.
NOTE:

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

  1. Enter the system view.

    system-view

  2. 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.

  3. 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

  1. Enter the system view.

    system-view

  2. Enable the DHCP server to respond to BOOTP requests.

    dhcp server bootp

    By default, a DHCP server does not respond to BOOTP requests.

  3. 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) Disabling the Function of Checking Abnormal Messages

Context

Devices from different vendors may use different DHCP implementation mechanisms. After checking the UDP header checksum or magic-cookie field in a received DHCP message, a device may not allow the DHCP message to pass through and discards the message. As a result, DHCP becomes unavailable. To solve this problem, you can disable the function of checking abnormal messages to allow the device to properly forward a DHCP message with an incorrect UDP header checksum or an incorrect value in the magic-cookie field.

NOTE:
  • This function applies to DHCP servers, DHCP relay agents, DHCP clients, and DHCP snooping-enabled devices.
  • After DHCP is enabled, the device checks the IP header checksum and UDP header checksum of DHCP messages by default, and the function of checking the IP header checksum cannot be disabled.

Procedure

  • Disable the function of checking abnormal messages in the system view.
    1. Enter the system view.

      system-view

    2. Disable the function of checking abnormal messages.

      • Disable the function of checking the magic-cookie field in a DHCP message.

        undo dhcp anti-attack check magic-cookie

        By default, a device does not check the magic-cookie field in a DHCP message but directly forwards a DHCP message with an incorrect value in the magic-cookie field.

      • Disable the function of checking the UDP header checksum in a DHCP message.

        undo dhcp anti-attack check udp-checksum

        By default, a device checks the UDP header checksum in a DHCP message and discards a DHCP message with an incorrect checksum.

  • Disable the function of checking abnormal messages in the VLAN view.
    1. Enter the system view.

      system-view

    2. Enter the VLAN view.

      vlan vlan-id

    3. Disable the function of checking abnormal messages.

      • Disable the function of checking the magic-cookie field in a DHCP message.

        undo dhcp anti-attack check magic-cookie

        By default, a device does not check the magic-cookie field in a DHCP message but directly forwards a DHCP message with an incorrect value in the magic-cookie field.

      • Disable the function of checking the UDP header checksum in a DHCP message.

        undo dhcp anti-attack check udp-checksum

        By default, a device checks the UDP header checksum in a DHCP message and discards a DHCP message with an incorrect checksum.

  • Disable the function of checking abnormal messages in the interface view.
    1. Enter the system view.

      system-view

    2. Enter the interface view.

      interface interface-type interface-number

    3. Disable the function of checking abnormal messages.

      • Disable the function of checking the magic-cookie field in a DHCP message.

        undo dhcp anti-attack check magic-cookie

        By default, a device does not check the magic-cookie field in a DHCP message but directly forwards a DHCP message with an incorrect value in the magic-cookie field.

      • Disable the function of checking the UDP header checksum in a DHCP message.

        undo dhcp anti-attack check udp-checksum

        By default, a device checks the UDP header checksum in a DHCP message and discards a DHCP message 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

  1. Enter the system view.

    system-view

  2. 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.

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 }

      NOTE:

      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.

      NOTE:

      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, an address pool allocates IP addresses 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:

      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.

NOTE:

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

(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.

NOTE:
  • 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 IPSG Configuration in the S7700 and S9700 V200R013C00 Configuration Guide - Security), and static ARP. Table 3-8 lists different usage scenarios and implementations of these functions.
Table 3-8  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.

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.

NOTE:

The BOOTP client does not support the configuration of an address lease time.

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.

NOTE:

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.

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.

NOTE:

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

A DHCP server can allocate user-defined options to clients using the following methods:
  • Based on the options in DHCP Discovery messages

    Configure the options using the dhcp server option (based on an interface address pool) or option (based on a global address pool) command. The DHCP server provides options only if clients request them.

  • By forcibly appending the Options field

    Configure the options using the dhcp server force insert option (based on an interface address pool) or force insert option (based on a global address pool) command. The DHCP server inserts the Options field in a DHCP Reply message, regardless of whether clients request the options.

Procedure

  • Configure user-defined options for clients based on an interface address pool.
    1. Enter the system view.

      system-view 

    2. (Optional) Enable the DHCP server to trust Option 82.

      dhcp server trust option82

      By default, the device is enabled to trust Option 82.

    3. (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 does not check and discard DHCP messages with duplicate options.

    4. Enter the interface or sub-interface view.

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

    5. (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.

    6. (Optional) Force the DHCP server to insert an Option field into DHCP Reply messages.

      dhcp server force insert option code &<1-254>

      By default, the DHCP server does not forcibly insert an Option field to DHCP Reply messages.

      After this function is configured, the device inserts an Option field to a DHCP Reply message regardless of whether the option has been requested.

    7. Configure DHCP 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 option is configured.

      NOTE:

      If an option carries a password, using cipher is recommended. For security purposes, use a password that is at least six characters long and contains at least two of the following: digits, lowercase letters, uppercase letters, and special characters.

      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

      Option 1 Mask-length in the ip address ip-address { mask | mask-length } command. Subnet mask
      Option 3 Ip-address in the ip address ip-address { mask | mask-length } command. Gateway address
      Option 6 dhcp server dns-list ip-address &<1-8> DNS server IP address
      Option 15 dhcp server domain-name (interface view) domain-name Domain name
      Option 44 dhcp server nbns-list ip-address &<1-8> NetBIOS server IP address
      Option 46 dhcp server netbios-type { b-node | h-node | m-node | p-node } NetBIOS node type
      Option 50 N/A Requested IP address
      Option 51 dhcp server lease { day day [ hour hour [ minute minute ] ] | unlimited } IP address lease
      Option 52 N/A Additional option
      Option 53 N/A DHCP message type
      Option 54 N/A Server identifier
      Option 55 N/A Parameter request list
      Option 57 N/A Maximum length of a DHCP message
      Option 58 N/A Lease renewal time (T1), which is 50% of the lease time
      Option 59 N/A Lease renewal time (T2), which is 87.5% of the lease time
      Option 61 N/A Client identifier
      Option 82 N/A Relay agent information
      Option 121 dhcp server option121 ip-address { ip-address mask-length gateway-address } &<1-8> A group of classless routes
      Option 184 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:

      1. Enter the system view.

        system-view
      2. (Optional) Enable the DHCP server to trust Option 82.

        dhcp server trust option82

        By default, the device is enabled to trust Option 82.

      3. Enter the global address pool view.

        ip pool ip-pool-name
      4. (Optional) Force the DHCP server to insert an Option field into DHCP Reply messages.

        force insert option code &<1-254>

        By default, the DHCP server does not forcibly insert an Option field to DHCP Reply messages.

      5. Configure DHCP 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 option is configured.

        NOTE:

        If an option carries a password, using cipher is recommended. For security purposes, use a password that is at least six characters long and contains at least two of the following: digits, lowercase letters, uppercase letters, and special characters.

        Not all options can be configured using the preceding command. The following table lists the options and their commands.
        Table 3-10  Commands for configuring options

        Option

        Configuration Command

        Description

        Option 1 mask-length in the network (IP address pool view) ip-address [ mask { mask | mask-length } ] command Subnet mask
        Option 3 gateway-list ip-address &<1-8> Gateway address
        Option 6 dns-list ip-address &<1-8> DNS server IP address
        Option 15 domain-name domain-name Domain name
        Option 44 nbns-list ip-address &<1-8> NetBIOS server IP address
        Option 46 netbios-type { b-node | h-node | m-node | p-node } NetBIOS node type
        Option 50 N/A Requested IP address
        Option 51 lease { day day [ hour hour [ minute minute ] ] | unlimited } IP address lease
        Option 52 N/A Additional option
        Option 53 N/A DHCP message type
        Option 54 N/A Server identifier
        Option 55 N/A Parameter request list
        Option 57 N/A Maximum length of a DHCP message
        Option 58 N/A Renewal time (T1), which is 50% of the lease time
        Option 59 N/A Lease renewal time (T2), which is 87.5% of the lease time
        Option 61 N/A Client identifier
        Option 82 N/A Relay agent information
        Option 121 option121 ip-address { ip-address mask-length gateway-address } &<1-8> A group of classless routes
        Option 184 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 an Option field into DHCP Reply messages.

        force insert option code &<1-254>

        By default, the DHCP server does not forcibly insert an Option field to DHCP Reply messages.

      4. Configure DHCP 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 option is configured.

        NOTE:

        If an option carries a password, using cipher is recommended. For security purposes, use a password that is at least six characters long and contains at least two of the following: digits, lowercase letters, uppercase letters, and special characters.

        Not all options can be configured using the preceding command. See Table 3-10 for the list of options and their commands.

      5. Configure a classless static route to allocate to a DHCP client.

        option121 ip-address { ip-address mask-length gateway-address } &<1-8>

        By default, no classless static route 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.
Translation
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Updated: 2019-04-20

Document ID: EDOC1100065743

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