Using Manual Ima Group Restart; Using Automatic Ima Group Restart - Cisco MGX 8850 (PXM1E/PXM45) Configuration Manual

Managing IMA
In Figure
operating correctly. If different IMA group IDs are configured at each end of the IMA links (cnfimagrp
-txid), the switch can easily determine which links are in loopback and which links are connected to the
far end. If the received far-end ID is the same as the near-end ID, the link is in loopback. If the near and
far end IDs are different, the link is communicating with the far-end IMA group.
The following situations can require an IMA restart:
1.
2.
3.
A restart will correct the problem in all three of the situations described above if a different IMA group
Note
ID is configured for the near and far ends. If the same IMA group ID is configured at both ends, it is
possible that the links in loopback will respond first and the IMA group will not communicate with the
far end.
Cisco MGX switches allow you to manually restart an IMA group to correct communications problems.
Beginning with Release 5, you can also enable and configure the IMA autorestart feature, which will
automatically restart an IMA group when necessary. The following sections describe how to use the
manual and automatic restart features.

Using Manual IMA Group Restart

To manually restart an IMA group, enter the restartimagrp <bay.group> command. Replace bay with
the number 1 to specify the top bay, or 2 to specify the lower bay. Replace group with the IMA group
you want to restart (To display the configured IMA groups, enter the dspimagrps command).
After you enter the restartimagrp command, the IMA group attempts to re-establish the IMA protocol
with far end of a failed connection.
In the following example, the user attempts to restart the IMA group number 6 in the lower bay.
Unknown.7.PXM.a > restartimagrp 2.6

Using Automatic IMA Group Restart

The IMA autorestart feature is new for PXM1E-16-T1E1 in Release 5. To enable and configure the IMA
autorestart feature, use the following procedure.
Note The IMA autorestart feature is a Cisco enhancement to the IMA operation described in the IMA
specifications. The IMA specifications do not provide for the detection of lines in loopback mode and
for automatic restart.
Cisco MGX 8850 (PXM1E/PXM45), Cisco MGX 8950, Cisco MGX 8830, and Cisco MGX 8880 Configuration Guide
9-94
9-3, one link in IMA Group A is operating in loopback mode, and the other three lines are
All links are in loopback, and then individual links are connected to the remote end. In this scenario,
the IMA group is communicating with itself and must be restarted so that it will start communicating
with the far end.
One link is in loopback and the other links fail after successful communications have been
established with the far end. This situation creates an error condition for the IMA group which can
be cleared by restarting the IMA group and allowing the IMA group to communicate with itself over
the loopback link.
The failed links in situation 2 recover while the IMA group is communicating with itself. This is
really the same as situation 1. The IMA group must be restarted so that the IMA group can establish
communications with the far end.
Chapter 9 Switch Operating Procedures
Release 5.0.10, OL-3845-01 Rev. B0, August 16, 2004