Switches picking up wrong default gateway

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Dec 11th, 2008
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This one has me stumped. I have attached a jpg to show what is going on. Basically, EIGRP 20 redistributes the default route to the switches. However, the switches are picking on the FE interface of our VOIP gateway. It should be picking up the GI0/0 interface of the router. This is causing an extra hop and can't determine why this is happening.



Correct Answer by Richard Burts about 8 years 5 months ago

Jason


I do not have enough of the details to fully explain what is happening. But I think that I see part of it. EIGRP 20 is advertising the route over both VLAN 60 and VLAN 70. The voice gateway appears to participate in EIGRP on both VLANs and has chosen as its default route the path through VLAN 70. This implies that the advertisement on VLAN 70 has a more attractive metric than the path on VLAN 60. And since the preferred route on the voice gateway was learned on VLAN 70 it then advertises it out VLAN 60 and with a metric that is probably still more attractive. You could probably confirm this with the output of show ip eigrp topology for the 0.0.0.0 route from both routers.


Based on what I think I understand about the issue I would suggest that you could configure an outbound offset list on the WAN router on the Gig0/1 interface to boost the metric of the default route and make it less attractive than what is advertised out Gig0/0.


HTH


Rick

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Richard Burts Thu, 12/11/2008 - 11:38
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Jason


I do not have enough of the details to fully explain what is happening. But I think that I see part of it. EIGRP 20 is advertising the route over both VLAN 60 and VLAN 70. The voice gateway appears to participate in EIGRP on both VLANs and has chosen as its default route the path through VLAN 70. This implies that the advertisement on VLAN 70 has a more attractive metric than the path on VLAN 60. And since the preferred route on the voice gateway was learned on VLAN 70 it then advertises it out VLAN 60 and with a metric that is probably still more attractive. You could probably confirm this with the output of show ip eigrp topology for the 0.0.0.0 route from both routers.


Based on what I think I understand about the issue I would suggest that you could configure an outbound offset list on the WAN router on the Gig0/1 interface to boost the metric of the default route and make it less attractive than what is advertised out Gig0/0.


HTH


Rick

jgorman1977 Fri, 12/12/2008 - 06:52
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Rick,


The strange thing I am not redistributing a default router from EIGRP 10, only from EIGRP 20. Is there a command to resync EIGRP?


Thanks,


Jason

Richard Burts Fri, 12/12/2008 - 11:46
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Jason


I am not sure what EIGRP 10 has to do with the issue. And not sure what your question is about resync EIGRP. And I am not really clear why you are running both EIGRP 10 and EIGRP 20 (but I do not believe that has much to do with this issue).


What I believe is that EIGRP 20 is running on both VLAN 60 and VLAN 70 and advertising the default route on both VLANs. And that the voice gateway has selected the path through VLAN 70 and is advertising it on VLAN 60. Beyond that there is not enough information provided to do useful analysis.


HTH


Rick

jgorman1977 Mon, 12/15/2008 - 06:24
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Rick,


The offset-list was the trick. Thanks for the help.

Richard Burts Mon, 12/15/2008 - 09:09
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Jason


I am glad that my suggestion of using an offset list helped you solve the issue. Thank you for using the rating system to indicate that your problem was resolved (and thanks for the rating). It makes the forum more useful when people can read about a problem and can know that they will see suggestions that did lead to the solution of the problem.


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


HTH


Rick

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