Next hop inaccessible for Cisco Nexus

Vendor

Cisco

Description

Indeni will review the routing table and identify when a next hop router is showing as FAILED or INCOMPLETE in the ARP table.

Remediation Steps

Determine why the next hops are not responding.

1. Execute the "show spanning-tree" and "show spanning-tree summary" NX-OS commands to quickly identify the STP root for all the configured vlans.

2. Run the "show spanning-tree vlan X detail" NX-OS command to collect more info about the STP topology (X=vlanid).

3. Check the event history to find where the Topology Change Notifications originate from by running the next NX-OS command "show spanning-tree internal event-history tree X brief" , (X=vlanid).

4. Display the STP events of an interface with the next NX-OS command "show spanning-tree internal event-history tree Y interface X brief" , (X=vlanid, Y=interfaceid).

5. Consider to hard code the STP root and backup root to the core switches by configuring a lower STP priority.

6. Activate the recommended vPC "peer switch" NX-OS command to a pure peer switch topology in which the devices all belong to the vPC.

7. Consider to use Root Guard feature to enforce the root bridge placement in the network. If a received BPDU triggers an STP convergence that makes that designated port become a root port, that port is put into a root-inconsistent (blocked) state.

8. For more information please review the following links:

Spanning Tree Protocol Troubleshooting on a Nexus 5000 Series Switch

Spanning Tree Design Guidelines for Cisco NX-OS Software and Virtual PortChannels

How does this work?

This script logs into the Cisco Nexus switch using SSH and retrieves the output of the "show ip route static" command. The output includes a table with the device's configured static routes.

Why is this important?

This script logs into the Cisco Nexus switch using SSH and retrieves the output of the "show ip route static" command. The output includes a table with the device's configured static routes.

Without Indeni how would you find this?

It is possible to poll this data through SNMP but additional external logic would be required to correlate the static routes table across vPC domain (cluster) members.


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