Alcatel-Lucent 7750 SR - Linktrace; Figure 28: CFM Linktrace

Services
7750 SR OS Services Guide Page 105
Linktrace
A linktrace message is originated by an MEP and targeted to a peer MEP in the same MA and
within the same MD level (Figure 28). Its function is similar to IP traceroute.
Traces a specific
MAC address through the serviceThe peer MEP responds with a linktrace reply message after
successful inspection of the linktrace message. The MIPs along the path also process the linktrace
message and respond with linktrace replies to the originating MEP if the received linktrace
message has a TTL greater than 1 and forward the linktrace message if a look up of the target
MAC address in the Layer 2 FIB is successful. The originating MEP shall expect to receive
multiple linktrace replies and from processing the linktrace replies, it can put together the route to
the target bridge.
A traced MAC address is carried in the payload of the linktrace message. Each MIP and MEP
receiving the linktrace message checks whether it has learned the target MAC address. In order to
use linktrace the target MAC address must have been learned by the nodes in the network. If so, a
linktrace message is sent back to the originating MEP. Also, a MIP forwards the linktrace message
out of the port where the target MAC address was learned.
The linktrace message itself has a multicast destination address. On a broadcast LAN, it can be
receved by multiple nodes connected to that LAN. But, at most, one node will send a reply.
Figure 28: CFM Linktrace
Fig_13
MEP1
MEP1 MEP3MEP2 MEP5
MEP11
Linktrace Reply
Messages to
MEP1
Linktrace Request
Messages
MEP4 MEP7
Bridge
Port
MIP
MEP
MEP6 MEP8
MEP10 MEP3
MEP2 MEP12
MEP4