Swith Not Passing Traffice

Unanswered Question
Apr 25th, 2008

I have an interesting issue. I have a 6509 running IOS image s72033-advipservicesk9_wan-mz.122-18.SXF6.bin. After I configure an IP address on a new loopback interface on this device it stops passing traffice. Nothing in the logs indicate anything out of the orindary. Once I remove the IP address it starts passing traffic.


I have this problem too.
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Richard Burts Fri, 04/25/2008 - 07:45


Some additional information would be helpful. To start with what address and mask are you configuring on the loopback? Also you saying that it passes no traffic at all?

What kind of routing information is the switch using? Is it static routing, dynamic routing protocol? What do the contents of the routing table look like before you configure the loopback and what is in the routing table after you configure the loopback with its IP address?



chuck.gilkes Fri, 04/25/2008 - 09:14

I applied /32 from a listed of addresses we have reserved for loopbacks. This switch is running two instances of OSPF. And, iBGP. I did not look at the routing tables before or after.

That's correct, no traffic period, with exception of out of band, console port, traffic. I thought perhaps I had a IP address conflict. I then assigned an IP that I was 100 percent sure would not conflict any of our address space and saw the same results.

Richard Burts Fri, 04/25/2008 - 09:41


When you tell us that the switch is running 2 instances of OSPF I wonder if the loopback address might be impacting the OSPF processes. OSPF will prefer a loopback interface as its RID. Once the OSPF process starts (and selects its RID) it should not be impacted by interface changes. But I wonder if something is going on there.

Can you re-create the problem? If so I would like to see the output of show ip ospf and of show ip route from before the change and again after the change.




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