Service Manual

Sending Linktrace Messages and Responses
Linktrace message and response (LTM, LTR), also called Layer 2 Traceroute, is an administratively sent multicast frames transmitted
by MEPs to track, hop-by-hop, the path to another MEP or MIP within the maintenance domain.
All MEPs and MIPs in the same domain respond to an LTM with a unicast LTR. Intermediate MIPs forward the LTM toward the
target MEP.
Figure 5. MPLS Core
Link trace messages carry a unicast target address (the MAC address of an MIP or MEP) inside a multicast frame. The destination
group address is based on the MD level of the transmitting MEP (01:80:C2:00:00:3[8 to F]). The MPs on the path to the target
MAC address reply to the LTM with an LTR, and relays the LTM towards the target MAC until the target MAC is reached or TTL
equals 0.
• Send a Linktrace message. Because the LTM is a Multicast message sent to the entire ME, there is no need to specify a
destination.
EXEC Privilege
traceroute ethernet domain
Caching Link Trace
After you execute a Link Trace command, the trace information can be cached so that you can view it later without retracing.
To enable, set, display, and delete link trace caching, use the following commands.
• Enable Link Trace caching.
CONFIGURATION mode
traceroute cache
• Set the amount of time a trace result is cached.
ETHERNET CFM mode
traceroute cache hold-time minutes
The default is 100 minutes.
The range is from 10 to 65535 minutes.
802.1ag
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