L2 Traceroute

The l2 traceroute command is a proprietary command that allows you to trigger an LTM message. Use this command as follows:

For B-VLANs, specify either the destination MAC address or node name.
For C-VLANs, specify the destination MAC address.

This command provides a simpler command syntax than the standard LTM commands, which require the user to specify the MD, MA, and MEP ID information. The l2 traceroute command provides a trace equivalent at Layer 2 for use with nodes on the SPBM B-VLAN in the customer domain.

Important

Only the VSP 4450 Series switch supports CFM configuration on C-VLANs.

CFM CMAC L2 ping and L2 traceroute traversing over Fabric Extend tunnels are not supported when originating from a VSP 4450 Series.

You can use CFM to troubleshoot networks and hosts that support the CFM protocol. After you configure CFM, CFM works in the network whether or not SPBM is in use.

You cannot use CFM to troubleshoot networks and hosts that do not support the CFM protocol, such as a customer domain that does not support CFM. Only devices that support the CFM protocol respond to l2 ping and l2 traceroute requests.

l2 traceroute with IP address

The l2 traceroute command allows you to specify an IP address as the destination address. In this case, the IP address can be either a C-VLAN or a B-VLAN in the SPBM cloud.

The l2 traceroute command converts Layer 3 IP information to an appropriate Layer 2 VLAN and MAC combination. The system can also target IP addresses that are not SPBM derived routes.

If ECMP is enabled, l2 traceroute runs internally for each of the VLAN paths returned, and displays a summary of the results. If ECMP is disabled, the results display only one path.

Note

If you use the l2 traceroute ip-address command on a DvR Leaf node, the output only shows DvR Controller IP addresses if the IP address or host route specified is unknown in the DvR domain.

Destination addresses for C-VLAN l2 traceroute and linktrace messages

For C-VLANs, CFM uses the following destination MAC addresses for the corresponding maintenance domain (MD) levels for l2 traceroute and linktrace messages.

The switch supports both l2 traceroute and linktrace for C-VLANs, as a best practice, use l2 traceroute.

Table 1. **MD levels and corresponding destination addresses for CFM for C-VLANs**
CFM MD Level	Destination MAC address
0	01:80:c2:00:00:38
1	01:80:c2:00:00:39
2	01:80:c2:00:00:3a
3	01:80:c2:00:00:3b
4	01:80:c2:00:00:3c
5	01:80:c2:00:00:3d
6	01:80:c2:00:00:3e
7	01:80:c2:00:00:3f