Troubleshooting Ist Failure Using The Acli - Avaya 8800 Troubleshooting Manual

Layer 2 troubleshooting
3. Check interface status:

Troubleshooting IST failure using the ACLI

When interswitch trunk (IST) links are used, all critical network traffic runs this link. Therefore,
in the event of IST failure, network protocols like RIP, VRRP, OSPF, VLACP and so on go up
and down and eventually causes a network outage.
There are the possible reasons for IST failure:
• The IST had been disabled.
• An incorrect peer IP address is configured.
• The MLT does not have the proper ports configured.
• MLT ports are down.
Note:
When the VLACP protocol goes up and down (flaps) rapidly, this behavior can cause
system-wide instability, including high CPU utilization. For more information on how to
resolve VLACP flapping, see Avaya Ethernet Routing Switch 8800/8600 Configuration —
Link Aggregation, MLT, and SMLT (NN46205-518).
For a flowchart recovery tree, see
Procedure steps
1. Check IST settings:
2. Check MLT settings:
352 Troubleshooting
Verify that the correct ports are members of the MLTs, and that the trunk is
enabled.
show ip interface
show ports info all
Verify that, for each interface, the port state is enabled, and its operational state is
up. If they are not, try to disable then reenable the port. If the ports do not come up,
there may be a physical layer issue.
show ist mlt
If any settings are incorrect, make the correction.
show mlt <1-256>
Comments? infodev@avaya.com
IST failure on page 335.
July 2013