Command
Debug IP Routing
Use
This command enables debugging messages related to the routing table. This debug is particularly useful for finding routing loops. Since the routing table is normally stable, you will only see debug messges when there are route changes.
Syntax
Router#debug ip routing
Example
In the below example we enable debug ip routing.
R2(config)#do debug ip routing IP routing debugging is on R2(config)#
Now on R3, will we add a new interface under the OSPF process
R3(config)#do sh run | sec ospf router ospf 1 log-adjacency-changes network 0.0.0.0 255.255.255.255 area 0 R3(config)#int lo44 *Mar 1 19:45:07.287: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback44, changed state to up R3(config-if)#ip add 44.44.44.44 255.255.255.255
On R2 we can see the debug output for R2 adding the new OSPF route.
R2(config)# *Mar 1 01:19:06.195: RT: SET_LAST_RDB for 44.44.44.44/32 NEW rdb: via 10.2.2.3 *Mar 1 01:19:06.199: RT: add 44.44.44.44/32 via 10.2.2.3, ospf metric [110/2] *Mar 1 01:19:06.203: RT: NET-RED 44.44.44.44/32
Now on R3 we will remove the interface we added from the OSPF process.
R3(config-if)#no int lo44 On R2 we can see the debug output for R2 displaying the status messages related to deleting the new OSPF route.
R2(config)# *Mar 1 01:19:28.891: RT: del 44.44.44.44/32 via 10.2.2.3, ospf metric [110/2] *Mar 1 01:19:28.895: RT: delete subnet route to 44.44.44.44/32 *Mar 1 01:19:28.899: RT: NET-RED 44.44.44.44/32 *Mar 1 01:19:28.903: RT: delete network route to 44.0.0.0 *Mar 1 01:19:28.903: RT: NET-RED 44.0.0.0/8