Default Route Problem

[shufordm]

We are using 3750G switches to route traffic through our Metro Ethernet network. We have a hub and spoke topology but a few of our sites have secondary links to other sites for redundancy. The physical switch ports are all setup as layer 2 trunk links and we emplement layer 3 using vlan interfaces. We are also using EIGRP for routing. The default-route on each 3750G points back to the hub via the VLAN 21 interface.

Now here is my problem. We setup secondary links between some of the sites for redundancy so that traffic can get back to the hub in case the main link goes down at that site. When the actual physical Metro E link goes down I am finding that traffic for unknown networks are not being routed.

If I do a trace route the packets never leave the originating L3 switch. If I take down the physical link "and" shutdown the corresponding vlan interface the default route traffic will then go out the backup link.

What I need to figure out is how to get it to failover to the backup link when the physical link to Metro E goes down. Does anyone have any ideas that I can try?

Thanks!

[Richard Burts]

Mark

I am not sure that I have a good understanding of the order in which you made some of the changes. I think I understand that you made a change to have EIGRP at the hub to advertise the default route from the hub to the spokes. I am not clear at what point in the process of changes you removed the static default route from router2. This is significant because as long as router2 has a local default route, even if it receives an advertisement of the default from the hub it will not advertise the default to router1. So the changes need to include having the hub advertise the default route to all spokes and removing the local default route from all spokes (especially from spokes with backup links).

The configs that you posted for router1 and router2 look to me like they should work (since neither spoke has a local default route). It might help to confirm this if you would post the output of show ip eigrp topology from router1.

HTH

Rick

[shufordm]

Richard I removed both static routes from the spokes after I told the hub to redistribute. I will post the topology tomorrow morning.

[shufordm]

Richard thanks for the help. Your initial post was the correct solution. It seems that the reason I was still have problems after making the changes was because the switch was faulty. It had been freezing regularly and actually froze after our troubleshooting the other day. I swapped it out with another 3750G and put the same exact config on it that we were using before and everything started working the way that it should be.

[Richard Burts]

Mark

I am glad that you got it worked out and that my suggestion was helpful. Thanks for posting back indicating that you had solved the problem and what the solution was. It is interesting that there were actually 2 problems (a configuration issue and a hardware issue) and that frequently makes the symptoms confusing.

The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.

HTH

Rick