Troubleshooting Routing

About Troubleshooting Routing Issues

Layer 3 routing involves determining optimal routing paths and packet switching. You can use routing algorithms to calculate the optimal path from the router to a destination. This calculation depends on the algorithm selected, route metrics, and other considerations such as load balancing and alternate path discovery.

Cisco NX-OS supports multiple virtual routing and forwarding (VRF) instances and multiple routing information bases (RIBs) to support multiple address domains. Each VRF is associated with a RIB, and this information is collected by the Forwarding Information Base (FIB).

See the following documents for more information on routing:

  • Cisco Nexus 9000 Series NX-OS Unicast Routing Configuration Guide

  • Cisco Nexus 9000 Series NX-OS Multicast Routing Configuration Guide

Initial Troubleshooting Routing Checklist

You can troubleshoot routing issues by checking these items first:

Checklist Done
Verify that the routing protocol is enabled.
Verify that the address family is configured if necessary.
Verify that you have configured the correct VRF for your routing protocol.

Use the following commands to display routing information:

  • show ip arp

  • show ip traffic

  • show ip static-route

  • show ip client

  • show ip fib

  • show ip process

  • show ip route

  • show vrf

  • show vrf interface

Troubleshooting Routing

SUMMARY STEPS

  1. switch# show ospf
  2. switch# show running-config eigrp all
  3. switch# show running-config eigrp
  4. switch# show processes memory | include isis
  5. switch# show ip client pim
  6. switch# show ip interface loopback-interface
  7. switch# show vrf interface loopback -interface
  8. switch# show routing unicast clients
  9. switch# show forwarding distribution multicast client

DETAILED STEPS

  Command or Action Purpose

Step 1

switch# show ospf

Example:

switch# show ospf 
                      ^ 
% invalid command detected at '^' marker.

Verifies that the routing protocol is enabled.

If the feature is not enabled, Cisco NX-OS reports that the command is invalid.

Step 2

switch# show running-config eigrp all

Example:

switch# show running-config eigrp all

Verifies the configuration for this routing protocol.

Step 3

switch# show running-config eigrp

Example:

switch# show running-config eigrp
version 6.1(2)I1(1) 
feature eigrp 
router eigrp 99 
  address-family ipv4 unicast 
    router-id 192.0.2.1 
  vrf red 
    stub

Verifies the VRF configuration for this routing protocol.

Step 4

switch# show processes memory | include isis

Example:

switch# show processes memory | include isis 
 8913   9293824  bffff1d0/bffff0d0  isis 
32243   8609792  bfffe0c0/bfffdfc0  isis

Checks the memory utilization for this routing protocol.

Step 5

switch# show ip client pim

Example:

switch# show ip client pim 
  Client: pim, uuid: 284, pid: 3839, extended pid: 3839 
  Protocol: 103, client-index: 10, routing VRF id: 255 
  Data MTS-SAP: 1519 
  Data messages, send successful: 2135, failed: 0

Verifies that the routing protocol is receiving packets.

Step 6

switch# show ip interface loopback-interface

Example:

switch# show ip interface loopback0 
loopback0, Interface status: protocol-up/link-up/admin-up, iod: 36, Context:"default" 
  IP address: 1.0.0.1, IP subnet: 1.0.0.0/24 
  ... 
  IP multicast groups locally joined: 
      224.0.0.2  224.0.0.1  224.0.0.13 
  ...

Verifies that the routing protocol is enabled on an interface.

Step 7

switch# show vrf interface loopback -interface

Example:

switch# show vrf interface loopback 99 
Interface                     VRF-Name                    VRF-ID 
loopback99                    default                          1

Verifies that the interface is in the correct VRF.

Step 8

switch# show routing unicast clients

Example:

switch# show routing unicast clients

Verifies that the routing protocol is registered with the RIB.

Step 9

switch# show forwarding distribution multicast client

Example:

switch# show forwarding distribution multicast client
Number of Clients Registered: 3 
Client-name  Client-id  Shared Memory Name 
igmp         1          N/A 
mrib         2          /procket/shm/mrib-mfdm

Verifies that the RIB is interacting with the forwarding plane.

Example

This example shows how to display the EIGRP routing protocol configuration: 


switch# show running-config eigrp all 
version 6.1(2)I1(1) 
feature eigrp 
router eigrp 99 
log-neighbor-warnings 
  log-neighbor-changes 
  log-adjacency-changes 
  graceful-restart 
  nsf 
  timers nsf signal 20 
  distance 90 170 
  metric weights 0 1 0 1 0 0 
  metric maximum-hops 100 
  default-metric 100000 100 255 1 1500 
  maximum-paths 16 
  address-family ipv4 unicast 
    log-neighbor-warnings 
    log-neighbor-changes 
    log-adjacency-changes 
    graceful-restart 
    router-id 192.0.2.1 
    nsf 
    timers nsf signal 20 
    distance 90 170 
    metric weights 0 1 0 1 0 0 
    metric maximum-hops 100 
    default-metric 100000 100 255 1 1500 
    maximum-paths 16
This example shows how to display that the unicast routing protocol is registered with the RIB: 


switch# show routing unicast clients 
CLIENT: am 
 index mask: 0x00000002 
 epid: 3908      MTS SAP: 252       MRU cache hits/misses:        2/1 
 Routing Instances: 
  VRF: management        table: base 
 Messages received: 
  Register          : 1      Add-route         : 2      Delete-route      : 1 
 Messages sent: 
  Add-route-ack     : 2      Delete-route-ack  : 1 
CLIENT: rpm 
 index mask: 0x00000004 
 epid: 4132      MTS SAP: 348       MRU cache hits/misses:        0/0 
 Messages received: 
  Register          : 1 
 Messages sent: 
... 
CLIENT: eigrp-99 
 index mask: 0x00002000 
 epid: 3148      MTS SAP: 63775     MRU cache hits/misses:        0/1 
 Routing Instances: 
  VRF: default           table: base                notifiers: self 
 Messages received: 
  Register          : 1      Delete-all-routes : 1 
 Messages sent: 
...

Troubleshooting Policy-Based Routing

  • Make sure the ACLs match the incoming traffic.

  • Make sure the route is available:

    • For IP network routes, use the show ip route command to make sure the IP network route is available for the next hop specified in the set ip next-hop command.

    • For IP host routes, use the show ip arp command to make sure the IP host route is available for the next hop specified in the set ip next-hop command.

    • For IPv6 network routes, use the show ipv6 route command to make sure the IPv6 network route is available for the next hop specified in the set ipv6 next-hop command.

    • For IPv6 host routes, use the show ipv6 neighbor command to make sure the IPv6 host route is available for the next hop specified in the set ipv6 next-hop command.

  • Make sure the policy is active in the system (using the show ip policy command).

  • Check the statistics for the entry (using the show route-map map-name pbr-statistics command).