OSPF neighbor(s) down for Cisco Nexus

Vendor

Cisco

Description

Indeni will alert if one or more OSPF neighbors isn't communicating well.

Remediation Steps

Review the cause for the neighbors being down.
This issue might be caused by:
a. L2/L3 connectivity issue
b. OSPF not being enabled on the interface
c. an interface is defined as passive
d. a mismatched subnet mask
e. a mismatched hello/dead interval
f. a mismatched authentication key
g. a mismatched area ID
i. a mismatched transit/stub/Not-So-Stubby Area (NSSA) option
Check OSPF configuration:
Use these commands in order to check the OSPF configuration (subnet, hello/dead interval, area ID, area type, authentication key (if any), and not-passive), and ensure that it matches on both sides.
a. "show run ospf"
b. "show ip ospf PID interface"
c. "show ip ospf PID"

Troubleshooting OSPF States:
1. OSPF Neighbor Stuck in the Initialization (INIT) State. This issue might be caused by:
a. one side is blocking the hello packet with ACL
b. one side is translating, with Network Address Translation (NAT), the OSPF hello
c. the multicast capability of one side is broken (L2)

2. OSPF Neighbor Stuck in a Two-Way State. This issue might be caused by OSPF priority set equal to zero.
NOTE: It is normal in broadcast network types.

3. OSPF Neighbor Stuck in Exstart/Exchange. This issue might be caused by:
a. MTU mismatch
b. Neighbor Router ID (RID) is the same as its neighbor's
c. ACL blocking unicast - after two-way OSPF sends unicast packet

4. OSPF Neighbor Stuck in a Loading State. This issue might be caused by bad Link State Advertisement (LSA). Check the OSPF-4-BADLSATYPE message with the "show ip ospf bad" and the "show log" commands.

Further details can be found in: CISCO Nexus OSPF troubleshooting guide
.

How does this work?

This script logs into the Cisco Nexus switch using SSH and retrieves the OSFP neigborship state using the "show ip ospf neighbor" command. The output includes a complete report of the per-neighbor OSPF state.

Why is this important?

Check if OSPF neighbors are up. If an adjacency disappears an alert will be triggered.

Without Indeni how would you find this?

It is possible to poll this data through SNMP. State transitions generate a syslog event.

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