2 default-gateways and 1 EIGRP process

[Mark Mattix]

I was wondering if someone could offer advice on how I should setup my EIGRP routing process. I have a simple network of R0---R1---R2---R3.

Currently R2 has a static 0.0.0.0 default route to R3 to the Internet. R2 has an EIGRP process setup with R0 and R1 to redistribute this static default route for Internet access. Soon R1 will get it's own Internet connection so R1 and R0 will connect to the internet on R1 and no longer through R3.

My question is, how can I implement this new Internet route on R1 without affecting the default gateway on R2 (which is via R3). In my lab I changed the bandwidth metric on R1 going to R2 lower than the bandwidth metric of the new Internet line. This didn't seem to make any difference in the routing table, R1 was still using the default route learned via R2's EIGRP process.

Thanks for any advice!  -Mark

[blau grana]

IP SLA will verify if internet link is working, if yes static route will be injected to routing table [no higher admin distance or whatever, just ip route 0.0.0.0 0.0.0.0 interface_wan ]

under router eigrp you will redistribute static routes, so if default route will be injected, you will redistribute it into eigrp process and advertise to all neighbors -> this set up will be same on R1&R3.

on both sides of link between R1&R2 you will increase delay on interface so local routes will be prefered. Same thing you can do with bandwidth but it is not recommended cause changing bandwidth can influence a lot of other things.

If one of internet link fails, default route for that link will be flushed from routing table by local IP SLA and remote default route will be used as backup even cost is high, but it is only one so it is a winner.

Best Regards

Please rate all helpful posts and close solved questions

[Mark Mattix]

Thanks for your help blau_grana, I have a question to "on both sides of link between R1&R2 you will increase delay on interface so local routes will be prefered. "

My question is, if R2 has a default static route to the internet link on R3 this AD value will always be used before it would even check for metrics on the EIGRP routes, correct? If R1 has a static route being injected by IP SLA this AD value will also be 1 so it wouldn't use the EIGRP route to R2>R3. Although, if IP SLA on R1 couldn't contact the internet than it would remove the static route and continue to use the EIGRP route.

So basiaclly what I'm asking is, it seems like if I only use IP SLA it should work exactly how I want it to function, without changing any metrics for EIGRP. Unless I'm missing something else? I appreciate your advice!

[blau grana]

Mark, you are right, if internet link is working on R1, R1 and routers behind him will always use that route because of AD

1 [static] < 170 [eigrp external]

Also if internet link on R3 is working, R3 router will always use this route.

But problem could be with R2 router. R2 will receive two default routes over EIGRP [EIGRP external AD 170==170 from R1 and R3] so R2 will decide based on metric which route will use. So based on your config R2 could use R1 as default gateway even if route via R3 is working. It would be better to take care of this possibility and increase delay on VPN link.

Best Regards

Please rate all helpful posts and close solved questions

[Mark Mattix]

Thanks for your help, blau_grana. R2 has a static route to R3 so I believe it should be ok. I will remember your recommendation of changing the delay values on the VPN link though. Thanks again!  -Mark

[paul driver]

Hello Mark
possible alternative!

Router 1
-----------
Track 1 interface (new wan link) ip-routing
Delay down 30
Delay up 30

Ip route 0.0.0.0 0,0,0,0 (new wan link) track 1 1
Ip route 0.0.0.0 0,0,0,0 (existing wan link) 2

Int xx (interface facing router2)
Ip summary- address eigrp xxx 0.0.0.0. 0.0.0.0.0 1


Res
Paul


Sent from Cisco Technical Support iPad App

[paul driver]

guys instead of messing with the delay how about manipulating the admin.distances ?
roiter eigrp
distance eigrp 90 171 (advertisting router) 1

acceess-list 1 permit x.x.x.x.

res
paul


Sent from Cisco Technical Support Android App