Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Community Member

Sending an EIGRP default-route with EIGRP stub routing and DMVPN backup

Senario:

(refer to attachment for network diagram)

You want to send an EIGRP default-route to remote sites (preferably using a distribute-list from the main site hub router) to shrink the routing tables at the remotes. You have a main site with remote branches connected as EIGRP stubs. The remote sites are connected via P2P T-1's. The remote sites connect to a hub router at the main site. In addition at the remote sites you have a DSL connection available as a backup link in case the T-1's go down. At the main site you have a routing being used only to terminate the DMVPN connections of the remotes.

Since the remote sites all have 2 conenctions to the main site (T-1 and DMVPN backup DSL) what would the best solution to send the default route to the remotes and also have the T-1's as being the "successors" while the backup DSL will be the "fe successors?

9 REPLIES

Re: Sending an EIGRP default-route with EIGRP stub routing and D

I would:-

1) Control the distribution of the default route inbound and outbound (You don't want a remote site sending you back the default route" to the remote sites via distribute lists.

2) I would control the "priorities" of the connections to the T-1 and the DMVPN by manipulating the EIGRP "Delay" and "Bandwidth" to the remote sites.

HTH>

Hall of Fame Super Gold

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Brandon

I believe that you do not need to worry much about a distribute list on the remote to prevent advertisement of the default route back to the head end. If the remote is configured as a stub then it will accept advertisement from multiple upstream routers but it will not advertise back what it has learned dynamically. The essence of an EIGRP stub router is that is will advertise only local networks, connected subnets, or local static routes.

I would suggest that you might set priorities by using an offset list in the head end routers to make the metric of the backup route worse than the metric of the primary route. (effectively that is the same as manipulating the delay parameter). I believe that this would be better than manipulating the bandwidth.

HTH

Rick

Community Member

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Rick,

Thanks for you input. Do you see it possible to advertise a defaulr-route to the main site L3 swith to the HUB router? Then from the main site HUB router have a default-route down to the remote site routers? This is also since the HUB routers only have one connection into the main site.

Thanks

Hall of Fame Super Gold

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Brandon

Perhaps we are getting confused with some ambiguity in terminology. Your original post seems to talk about 2 "hub" routers at the main site. One "hub" connects to the remotes via T1 and the other "hub" connects to the remotes via DSL/DMVPN.

I do not understand which "hub" you are asking about in this current question. Perhaps you can help me understand your question better?

HTH

Rick

Community Member

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Rick,

Sorry for my mess of confusion. Perhaps this will be more clear?

Would it be possible to have the "main site L3 switch (we will call this the core switch)" send a default-route to the "main site HUB router (directly connected)", then have that HUB router send a default-route on to the "remote site stub routers"? I am trying to see if it is possible to just have an EIGRP default-route on BOTH the main site HUB router and the remote site stub routers, and not just a default-route on the remote site stub routers (since the HUB would normally send the default-route). I would like to shrink the routing tables on both the main site HUB router and the remote stubs ( to hopefully just a single default-route). I do think this is possible, I am just not sure how to set the AD's since I have a backup route/link (DMVPN) at the remote stubs?

Thanks

Hall of Fame Super Gold

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Brandon

I am still having some difficulty in getting clear about the question. When you talk about the hub router, is that the router with the serial links to the remotes, the router with the DSL/DMVPN connection to the remotes, or both?

But based on the clarification in this post, let me make these points:

- it is possible to have the core switch generate a default route and advertise it to the hub(s).

- it is possible to have the hub(s) advertise their learned default route to the remote.

- the remote can learn a default route from the hub(s).

- the routing table on the remote can be reduced so that it contains only the connected subnets and the default route.

- while you could reduce the routing table on the hub somewhat you are not able to reduce the routing table on the hub as much as you can reduce it on the remote. The remote can work fine with just its connected subnets and a default route. The hub must have its connected subnets, it must have the default route, and it must have all the subnets advertised by all of the remotes. We would need to know more about the environment to know whether the hub route would need other routes in its routing table or not.

HTH

Rick

Community Member

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Rick,

Your reply here really helps. When I mention hub router I am only referring to the router that connects all the serial (T-1's) to the remote sites. Sorry for not making that clear. Now in a configuration such as this how can you guarantee that the successor route will be that of the T-1's and not over the backup DMVPN connection since you want that connection to be the FE?

Thanks

Hall of Fame Super Gold

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Brandon

I am glad that we are making progress in understanding this. If you want to ensure that the default from the serial hub is the successor route and the DSL/DMVPN default is the feasible successor you may need to manipulate the advertised metric to make the DSL/DMVPN route worse than the serial route. (note that this may happen naturally since in general the bandwidth and delay of a T1 are better than the bandwidth and delay of a tunnel - at least they are on the routers that I checked) If you want to manipulate the metric I would suggest configuring an offset list to add to the metric on the DSL/DMVPN interface.

HTH

Rick

Community Member

Re: Sending an EIGRP default-route with EIGRP stub routing and D

Rick,

Thanks once again for the outstanding reply! This is exactly what I need. I have a lab I can mostly try this setup with. Offset list is something I recently covered in my IE study guide! Maybe I'll get to try the feature it out in this senario?

Thanks again!

-Brandon

725
Views
9
Helpful
9
Replies
CreatePlease to create content