Installation and User Manual
EtherHaul
1200™
Page 94
EH-INST-02, Issue 4.0
7.2.8
Working with Linktrace Messages
Linktrace messages are multicast from an originating MEP to a target MAC (MIP or
MEP)/MEP ID, to verify the path between the two. Linktrace Reply messages (LTRs) are
unicast from the target (or MIPs on route) to the originating MEP. Receipt of an LTR
verifies the path.
Arriving LTRs are stored on a per-MEP basis in the LTR database, as shown in
Figure
7-13
.
Figure
7-13 Per-MEP LTR Storage Structure
LTRs are stored in ascending sequence number order and LTRs with the same sequence
number (i.e., replies to the same LTM) are grouped together.
Since storage is limited, arrival of a new message results in discarding older messages.
Entire groups that use the same sequence number are discarded.
Use the following command to display LTR database information:
show cfm ltr-db [{<md-idx-list> | all} [{<ma-idx-list> | all}
[{<mepid-list> | all} [{SN-list | all}]]]]
SN stands for the Sequence Number of the LTR message stored. This does not refer to
the real sequence number stored in the LTR header, but rather, to the relative SN which
is equal to Real SN modulo Maximum Allowed Number of SNs.
For example, if the maximum allowed number of stored LTRs (with different SNs) is 20,
then the Real SN = 807 is translated into the Relative SN = 7.
It is possible to specify more than one SN in the command by designating indexe d
objects. For more information, refer to
Designating Indexed Objects
on page 172.
Table
11-17
on page 208 lists and describes the LTR attributes.
