Troubleshooting Guide

• A MEP that is not the target but is on the path to the target
- Generates a reply as described above.
- It also sets one of the flags fields in the reply to indicate that it is the terminal MEP.
Link trace message — multicast
The multicast link trace message (LTM) can be used to trace the multicast tree from any node on
any I- SID using the nickname MAC address and the I-SID multicast address.
Specifying a multicast target address for an LTM allows for the tracing of the multicast tree
corresponding to that destination address (DA). With a multicast target every node that is in the
active topology for that multicast address responds with a Linktrace reply and also forwards the LTM
frame along the multicast path. Missing Linktrace replies (LTRs) from the nodes in the path indicate
the point of first failure.
This functionality allows you to better troubleshoot I-SID multicast paths in a SPBM network.
l2traceroute
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 4000 Series switch supports CFM configuration on C-VLANs.
Note:
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.
Operations and Management
January 2017 Troubleshooting 150
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