Using GMAC Trace to Monitor the Forwarding Path on a Layer 2 Network

Generic MAC (GMAC) trace can be used to monitor paths and locate faults in a part of or a whole network without configuring an MD, MA, or MEP.

Context

GMAC trace has principles similar to those of 802.1ag MAC trace. The difference is that a source device does not need to be a MEP, and a destination device does not need to be a MEP or MIP. In other words, GMAC trace can be implemented without the need to configure an MD, MA, or MEP on the source, intermediate, or destination device.

Enable the GMAC trace function on the source, intermediate, and destination devices.

Procedure

Run system-view
The system view is displayed.
Run trace mac enable
The GMAC trace function is enabled globally.

If the GMAC trace function is enabled:
- A source device starts the GMAC trace function by sending a linktrace message (LTM) to a destination device.
- After receiving the LTM, the destination device replies to the source device with a linktrace reply (LTR).
Run commit
The configuration is committed.

(Optional) In a VLAN scenario: Run trace mac mac-address vlan vlan-id [ interface interface-type interface-number | -t timeout ]^*

Paths on a VLAN are checked.

The following shows an example:

<HUAWEI> system-view 
[~HUAWEI] trace mac enable 
[*HUAWEI] commit 
[~HUAWEI] trace mac 00e0-fc23-3459 vlan 2
Tracing the route to 00e0-fc23-3459 over a maximum of 255 hops: 
------------------------------------------------------------------------------- 
Hops     Mac                Ingress                     Ingress Action      Relay Action
          Forwarded         Egress                      Egress Action                    
-------------------------------------------------------------------------------- 
1     00e0-fc12-3459      gigabitethernet0/1/9      IngOK                 RlyFDB 
      Forwarded            gigabitethernet0/1/1       EgrOK       
2     00e0-fc12-3457      gigabitethernet0/1/1       IngOK                RlyFDB         
      Forwarded            gigabitethernet0/1/0       EgrOk         
3     00e0-fc23-3459      gigabitethernet0/1/0       IngOK                RlyHit        
      Not Forwarded 
Info: Succeed in tracing the destination address 00e0-fc23-3459.

(Optional) In a VLL scenario: Run trace mac mac-address l2vc l2vc-id { raw | tagged } [ interface interface-type interface-number | { [ pe-vid pe-vid ce-vid ce-vid ] | [ dot1q-vlan vlan-id ] } | -t timeout | -h ] ^*

The VLL network connectivity is checked.

The following shows an example:

<HUAWEI> system-view 
[~HUAWEI] trace mac enable 
[*HUAWEI] commit
[~HUAWEI] trace mac 00e0-fc12-3458 l2vc 1 raw
Tracing the route to 00e0-fc12-3458 over a maximum of 255 hops:
 Hops  Host Name (IP Address)
       Mac             Ingress                   Ingress Action    Relay Action
       Forwarded       Egress                    Egress Action   
1     HUAWEIA (10.10.10.16)
      00e0-fc22-3459  GigabitEthernet0/1/9           IngOK             RlyFDB
      Forwarded       GigabitEthernet0/1/1.1         EgrOK               
2     HUAWEIB (10.10.10.13)
      00e0-fc12-3458  GigabitEthernet0/1/17           IngOK             RlyHit
      Not Forwarded 
Info: Succeeded in tracing the destination address 00e0-fc12-3458.

(Optional) In a VPLS scenario: Run trace mac mac-address vsi vsi-name [ interface interface-type interface-number | { [ pe-vid pe-vid ce-vid ce-vid ] | [ dot1q-vlan vlan-id ] } | -t timeout | -h ] ^*

The VPLS network connectivity is checked.

The following shows an example:

<HUAWEI> system-view 
[~HUAWEI] trace mac enable 
[*HUAWEI] commit 
[~HUAWEI] trace mac 00e0-fc12-3458 vsi vsi1 -h
Tracing the route to 00e0-fc12-3458 over a maximum of 255 hops:
 Hops  Host Name (IP Address)
        Mac             Ingress                   Ingress Action    Relay Action
        Forwarded       Egress                    Egress Action    
1     HUAWEIA (10.10.10.16)        
      00e0-fc22-3459  GigabitEthernet0/1/9           IngOK             RlyFDB
      Forwarded       GigabitEthernet0/1/1.1         EgrOK                
2     HUAWEIB (10.10.10.13)
      00e0-fc12-3458  GigabitEthernet0/1/17           IngOK             RlyHit
      Not Forwarded  
Info: Succeeded in tracing the destination address 00e0-fc12-3458.