1841 - "intrachassis" Failover

Unanswered Question

Hi, i've recently suceeded the following deployment:

2 x 1841 (Main Offices)(different ISP's on each one)

11 x 871 (Branch Offices)

I've used DMPVNP, using GRE(eigrp)/Ipsec tunnels for that, every 871 in the branch offices requires two tunnels, one heading a 1841 and the second one heading the other 1841, so i can get a suscessfull failover method when any of the ISP's in the Main site goes down.

My question is:

Is there any way to get the same failover topology using just one 1841 in the main site?

Is it possible to use only one 1841 alone with two different ISP's so if any of the two tunnels go down the other one keeps the branch offices up?

Thanks in advance,

I have this problem too.
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guibarati Tue, 09/25/2007 - 11:51

Yes, you have to way to configure that, the simple one is configuring 2 default routes with different cost for each one, the problem with this is in the case you have a ethernet link that will never take the interface down, in this case you can use the IP sla monitor function to acomplish this, just be aware of the IOS version, if any command is not supported it's because of your IOS version/router model, use this configuration:

ip sla monitor 10

! this is the gateway you are monitoring

type echo protocol ipIcmpEcho 201.91.149.X

ip sla monitor schedule 10 life forever start-time now

! the ip sla #10 must match the schedule #10

! add a route to reach the gateway or the host you are pinging for link test

ip route 201.91.149.x

!create a track and tie it with the IP sla #

track 10 rtr 10 reachability

!create a route map and put it inside the inside interface of the router or the tunnel in the case of DMVPN

route-map roteamento permit 100

match ip address pontelnk

set ip next-hop verify-availability 10 track 10

set ip next-hop

! This says the next hop for IPs matching access list pontelnk is if the trak # 10 is up, otherwise use the


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