Ospf Exstart/Exchange Problems; Bgp+ Troubleshooting; Neighbors Not Established Between The Bgp Peers - Avaya 8800 Troubleshooting Manual

OSPF ExStart/Exchange problems

Although both routers can recognize each other and have moved beyond 2-way state, the
routers can be stuck in the ExStart/Exchange state. To help troubleshoot ExStart/Exchange
problems, use the trace level 6 2 command. A mismatch in maximum transmission unit
(MTU) sizes between the routers usually causes this type of problem. For example, one router
could be set for a high MTU size and the other router's default value is a smaller value.
Depending on the size of the LSDB, the router with the smaller value may not be able to process
the larger packets and thus be stuck in ExStart/Exchange state. To avoid this problem, ensure
that the MTU size value for both routers match. This problem is usually encountered during
interoperations in networks with other vendor devices.
In the Avaya Ethernet Routing Switch 8800/8600 Software Release 3.2.0.0 and later, the
supported MTU size for OSPF is 1500 bytes by default. Incoming OSPF database description
(DBD) packets are dropped if their MTU size is greater than 1500 bytes. To allow the Avaya
Ethernet Routing Switch 8800/8600 to accept OSPF database description packets with a
different MTU size, enable mtu-ignore.
When mtu-ignore is set to enable, the MTU check on the incoming OSPF DBD packet is not
performed. The Avaya Ethernet Routing Switch 8800/8600 (Software Release 3.2.0.0 and
later) automatically checks for OSPF MTU mismatches.

BGP+ troubleshooting

The following sections provide information for troubleshooting BGP+ issues.
For additional information on BGP debugging commands, see
commands

Neighbors not established between the BGP peers

If neighbor states are not establishing BGP peers, use the following procedure to troubleshoot
the issue.
1. First check whether the neighbors are in established state or in active state:
2. If the neighbors are in the active state, then check the BGP configurations on both
Troubleshooting
on page 144 (CLI) and
show ip bgp summary (CLI or ACLI)
sides and check whether they mismatch in some cases.
show ip bgp conf (CLI or ACLI)
Using BGP debugging commands
BGP+ troubleshooting
Using BGP debugging
on page 234 (ACLI).
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