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TechNotes-Understanding and Configuring DHCP Emulation
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TechNotes-Understanding and Configuring DHCP Emulation

TechNotes-Understanding and Configuring DHCP Emulation

In a DHCP Emulation test, an access node simulates the DHCP client to implement remote acceptance for services that obtain IP addresses in DHCP mode (such as IPTV, IPoE, and VoIP services) and to locate faults.

DHCP Emulation Overview

In a DHCP emulation test, an access node emulates a DHCP client to apply for an IP address from a DHCP server. By doing so, the access node can test the connectivity between the access node and DHCP server and therefore the validity of DHCP configurations on the DHCP relay agent, DHCP agent, and DHCP server. In addition, the access node can ping a remote server to test the connectivity between them.

NOTE:
  • The access node can be an OLT, MDU, or ONT.
  • The remote server is an upstream network device, for example, an IPTV server or softswitch.
  • The difference between a DHCP emulation test and the actual DHCP process is the initiator. In a DHCP emulation test, the access node functions as the initiator; in the actual DHCP process, the user terminal (for example, a PC, STB, or VoIP service terminal) functions as the initiator.

Mainly used for deployment acceptance and fault locating, a DHCP emulation test resolves the known issues in the traditional method. For details, see Table 1-1.

Table 1-1 Comparison between the traditional method and DHCP emulation test

Application Scenario

Traditional Method

DHCP Emulation Test

Deployment acceptance

At the device installation site, a test instrument is connected to the device and the process of users going online in batches is emulated. Alternatively, a laptop is connected to the device to test services on each port. The O&M costs are high.

A remote node implements an acceptance test for services, which does not require site visits and reduces the O&M costs.

Fault locating

When a user reports a fault, the maintenance engineer cannot remotely locate the specific network segment in a timely manner. The maintenance engineer needs to ask for the user's cooperation or go to the user's house to locate the fault, bringing about inconvenience to the user and incurring high O&M costs.

Faults can be remotely located and the specific network segment can be quickly located. Then a work order is assigned to the corresponding maintenance engineer. In this way, the efficiency is improved and the O&M costs are reduced.

DHCP Emulation Principles

The principles of DHCP emulation.

Figure 1-1 Principles of DHCP emulation
  1. The maintenance engineer telnets the access node and starts a DHCP emulation test.
  2. The DHCP emulation process starts. Figure 1-2 shows the DHCP emulation process.
    1. DHCP interaction is implemented between the access node and DHCP server, which tests the link connectivity between them.
    2. After obtaining an IP address, the access node pings the remote server if hostip (a DHCP emulation parameter indicating the IP address of the remote server) is set. This tests the link connectivity between the access node and remote server.
    3. The DHCP emulation is completed and the DHCP emulation result is returned.
    Figure 1-2 DHCP emulation flow
  3. The maintenance engineer queries the DHCP emulation result.
  4. The maintenance engineer manually stops the DHCP emulation test to release system resources in a timely manner.
    NOTE:

    A DHCP emulation test automatically stops when the default timeout interval (210s) elapses and the emulation result will be deleted.

DHCP Emulation Usage Scenario

On an FTTx network, access nodes are close to user terminals and are widely deployed. In a DHCP emulation test, an access node emulates the DHCP client to implement remote acceptance for services that obtain IP addresses in DHCP mode (such as IPTV, IPoE, and VoIP services) and locate faults, which reduces the O&M costs.

FTTx Network Application Scenarios

Figure 1-3 shows typical application scenarios of DHCP emulation on an FTTx network.

Figure 1-3 Typical application scenarios of DHCP emulation on an FTTx network
NOTE:

In Figure 1-3:

  • Users 1 and 2 receive IP services (such as IPTV, IPoE, and VoIP services) and are authenticated through the BRAS.
  • User 1, an FTTH user, receives IP services through the ONT; user 2, an FTTB/FTTC user, receives IP services through the MDU.

When a user receives IPTV, IPoE, or VoIP services and implements deployment acceptance or fault locating through a DHCP emulation test, only the user terminals and remoter servers differ and the operation methods are the same. The following uses receiving IPTV services as an example.

When IPTV services are undergoing deployment acceptance or faulty:

  • If the STB cannot obtain an IP address, network connectivity between the STB and DHCP server is abnormal. Perform a DHCP emulation test on the access node device to test the connectivity of each network segment.
  • If the STB obtains an IP address successfully, network connectivity between the STB and DHCP server is normal. If users 1 and 2 still cannot watch IPTV programs, ping the remote server (for example, an IPTV server) to test the connectivity between the STB and remote server.

Fault Locating

Locate the fault based on the obtained DHCP emulation result, as shown in Table 1-2.

Table 1-2 Mapping between the emulation result and fault range

emulation Result

Description

Fault Scope

send packet fail

The access node failed to send packets to the DHCP server.

The access node is faulty.

DHCP server not found

After sending DHCP Discover packets, the access node did not receive response packets from the DHCP server.

The network segment between the access node and DHCP server is faulty.

DHCP server refuse request

The DHCP server rejected the DHCP request from the access node.

The DHCP server is faulty.

get IP overtime

After sending a DHCP request, the access node did not receive confirmation packets from the DHCP server.

The network segment between the access node and DHCP server is faulty.

get IP successful

The access node obtained an IP address from the DHCP server, indicating that the DHCP interaction was successful.

The possible fault scopes are as follows:

  • The network segment between the user terminal and access node is faulty.
  • The network segment between the BRAS and remote server is faulty.

all ping succeed

The access node succeeded in pinging all the specified remote servers.

The network segment between the user terminal and access node is faulty.

partial ping succeed

The access node succeeded in pinging some of the specified remote servers.

The network segment between the BRAS and remote server that failed to be pinged is faulty.

all ping fail

The access node failed to ping all the specified remote servers.

Network segments between the BRAS and all remote servers are faulty.

system resource not enough

On the access node, resources for DHCP emulation are insufficient.

On the access node, resources for DHCP emulation are insufficient.

unknown

-

-

Configuring DHCP Emulation

Context

Maintenance engineers can log in to the access node and perform DHCP emulation configurations through the CLI or NMS. The following uses operations through the CLI as an example.

  • For FTTB or FTTC scenario, a DHCP emulation test can be directly performed on the OLT or MDU.
  • For FTTH scenario, a DHCP emulation test can be started on the ONT through the OLT.

Procedure

  1. Run the simulate dhcp start command to start a DHCP emulation test.
  2. Run the display simulation dhcp command to query the specified DHCP emulation result.

    NOTE:

    When the default timeout interval (210s) for the DHCP emulation test elapses or the DHCP emulation test is manually stopped, the DHCP emulation result will be deleted. Therefore, after the DHCP emulation test is completed, query the DHCP emulation result in a timely manner.

    Locate the fault based on the obtained DHCP emulation result, as shown in Table 1-2.

  3. Run the simulate dhcp stop command to stop the DHCP emulation test.

Example

In the FTTB or FTTC scenario: Log in to the OLT or MDU and start a DHCP emulation test on it.

  • ID of the service port: 0
  • MAC address of the simulated server: 00e0-fc00-0001
  • Option 60: HW
  • Option 61 type corresponding to the option 61 field: 1; client ID: 00e0-fc00-0002
  • IP address of the to-be-pinged remote server: 192.168.3.99
  1. Start a DHCP emulation test.
    huawei(config)#simulate dhcp start service-port
    { service-portid<U><0,131071> }:0
    { mac-address<P> <XXX-XXX-XXX> }:00e0-fc00-0001
    { <cr>|host-ip1<K>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K>|option60<K>|o
    ption61<K>|user-vlan<K> }:option60
    { option60<S><Length 1-64> }:HW
    { <cr>|host-ip1<K>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K>|option61<K> }
    :option61
    { mac-addr<K>|string<K> }:mac-addr
    { mac_clientid<P><XXXX-XXXX-XXXX> }:00e0-fc00-0002
    { <cr>|host-ip1<K>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K> }:host-ip1
    { ipaddr1<I><X.X.X.X> }:192.168.3.99
    { <cr>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K>|overtime<K> }:
    
      Command:
              simulate dhcp start service-port 0 00e0-fc00-0001 option60 HW
    option61 mac-addr 00e0-fc00-0002 host-ip1 192.168.3.99
    
     Please check whether the input flow ID and MAC address are correct. Incorrect
    parameters may affect the services of normal users.
     You are suggested to use the MAC address of the actual user.
     Are you sure to continue?(y/n)[n]:y
  2. Query the DHCP emulation result.
    huawei(config)#display simulation dhcp
    { <cr>|service-port<K>||<K>|><K>|>><K> }:service-port
    { service-portid<U><0,131071> }:0
    { mac-address<P><XXXX-XXXX-XXXX> }:00e0-fc00-0001
    
      Command:
              display simulation dhcp service-port 0 00e0-fc00-0001
     Total : 1
     -----------------------------------------------------------------------------
     -------------------------------- common info --------------------------------
     FlowID                  : 0                                                  
     User MAC                : 00e0-fc00-0001                                     
     User VLAN               : 10                                                 
     Optin60                 : HW                                                 
     Option61 type           : 1                                                  
     Option61 client         : 00e0-fc00-0002                                     
     Simulate status         : finished                                           
     Simulate result         : all ping succeed                                   
     Simulate start time     : 2019-01-17 16:51:59+08:00                          
     User IP                 : 192.168.3.100/24                                   
     DHCP server IP          : 192.168.3.8                                        
     Primary DNS server IP   : -                                                  
     Secondary DNS server IP : -                                                  
     Relay gateway           : 0.0.0.0                                            
     Default gateway         : 192.168.3.201                                      
     -------------------------------- route info ---------------------------------
     Route:1  Destination IP : 192.168.5.0/24     Next hop IP : 192.168.3.66      
              Next hop MAC   : -                  Local interface : -             
     Route:2  Destination IP : 192.168.4.0/24     Next hop IP : 192.168.3.88      
              Next hop MAC   : 00e0-fc00-dbba     Local interface : Y             
     Route:3  Dstination IP  : -                  Next hop IP : -                 
              Next hop MAC   : -                  Local interface : -             
     --------------------------------- ping info ---------------------------------
     Host:1   IP : 192.168.3.99        Total count : 3     Succeed count : 3      
     Host:2   IP : -                   Total count : 0     Succeed count : 0      
     Host:3   IP : -                   Total count : 0     Succeed count : 0      
     Host:4   IP : -                   Total count : 0     Succeed count : 0      
     Host:5   IP : -                   Total count : 0     Succeed count : 0      
     -----------------------------------------------------------------------------
  3. Stop the DHCP emulation test.
    huawei(config)#simulate dhcp stop service-port 0 00e0-fc00-0001

In the FTTH scenario, log in to the OLT and start a DHCP emulation test on the ONT.

NOTE:

During the DHCP emulation, the IP address obtained can be used for multicast emulation.

  • ID of the subrack/slot/port of the OLT connected to the ONT: 0/3/0
  • ID of the ONT enabled with DHCP emulation: 1
  • VLAN ID in the VLAN tag in packets: 10
  • Option 61 type corresponding to the option 61 field: 0; client ID: user
  • IP address of the to-be-pinged remote server: 192.168.3.99
  • IP address of the multicast program: 224.1.1.1
  1. Issue commands on the OLT to start a DHCP emulation test on the ONT.
    huawei(config)#simulate dhcp start ont
    { frameid/slotid/portid<S><Length 5-18> }:0/3/0
    { ontid<U><0,255> }:1
    { eth<K>|outer-vlan<K>|untag<K>|vlan<K> }:vlan
    { vlanid<U><1,4095> }:10
    { <cr>|host-ip1<K>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K>|option60<K>|o
    ption61<K>|priority1<U><0,7>|usermac<K> }:option61
    { mac-addr<K>|string<K> }:string
    { string_clientid<S><Length 1-64> }:user
    { <cr>|host-ip1<K>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K> }:host-ip1
    { ipaddr1<I><X.X.X.X> }:192.168.3.99
    { <cr>|host-ip2<K>|host-ip3<K>|host-ip4<K>|host-ip5<K>|groupid<K> }:groupid
    {ip-addr<I><X.X.X.X>|<cr> }:224.1.1.1
    {igmp-version<K> }:igmp-version
    {v2<K>|v3<K>}:v2
    
      Command:
              simulate dhcp start ont 0/3/0 1 vlan 10 option61 string user host-ip1
     192.168.3.99 groupid 224.1.1.1 igmp-version v2
    
  2. Query the ONT DHCP emulation result.
    huawei#display simulation dhcp
    { <cr>|ont<K>|service-port<K>||<K>|><K>|>><K> }:ont
    { <cr>|frameid/slotid/portid<S><Length 5-18> }:0/3/0
    { ontid<U><0,255> } 1
    
      Command:
              display simulation dhcp ont 0/3/0 1
    -----------------------------------------------------------------------------
     -------------------------------- common info --------------------------------
     simulation instance     : F/S/P: 0/3/0  ONTId:1  ONTPort WAN
     simulation VLAN tag num : 1
     simulation outer VLANID : 10
     simulation inner VLANID : -
     Option60                : -
     Option61 type           : 0
     Option61 client         : user
     Simulate status         : finished                                           
     Simulate result         : succeed                                   
     Simulate start time     : 2013-01-17 15:49:20+09:00
     User IP                 : 192.168.3.100/24                                   
     DHCP server IP          : 192.168.3.99                                        
     Primary DNS server IP   : 10.72.55.81                                        
     Secondary DNS server IP : 10.72.255.100                                      
     Relay gateway           : 192.168.3.99                                       
     Default gateway         : 192.168.3.99                                       
     -------------------------------- route info ---------------------------------
     Route:1  Destination IP : 192.168.5.0/24     Next hop IP : 192.168.3.66      
              Next hop MAC   : -                  Local interface : -             
     Route:2  Destination IP : 192.168.4.0/24     Next hop IP : 192.168.3.88      
              Next hop MAC   : 00e0-fc00-dbba     Local interface : Y             
     Route:3  Dstination IP  : -                  Next hop IP : -                 
              Next hop MAC   : -                  Local interface : -             
     --------------------------------- ping info ---------------------------------
     Host:1    IP : 192.168.3.99        Total count : 3     Succeed count : 3
     Host:2    IP : -                   Total count : 0     Succeed count : 0
     Host:3    IP : -                   Total count : 0     Succeed count : 0
     Host:4    IP : -                   Total count : 0     Succeed count : 0
     Host:5    IP : -                   Total count : 0     Succeed count : 0
     -----------------------------------------------------------------------------
     -----------------------------------------------------------------------------
      Multicast group IP      : 224.1.1.1
      Multicast source IP     : -
      Multicast version       : IGMPv2
      Data rate(kbps)         : 1500
     ----------------------------------------------------------------------------
    
  3. Stop the ONT DHCP emulation test.
    huawei(config)#simulate dhcp stop ont 0/3/0 1

DHCP Emulation Reference Standards and Protocols

  • IETF RFC 2131: Dynamic Host Configuration Protocol
  • IETF RFC 1533: DHCP Options and BOOTP Vendor Extensions
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Updated: 2019-09-19

Document ID: EDOC1100105779

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