How can I switch between frame and ADSL upon failure

[davidbec]

The customer has a ADSL as well as a frame relay line. Both lines are up/up, and are in this state permanently.

The customer wants http traffic routed to the ADSL, and all else on the frame relay.

If the ADSL goes down, they would like ALL traffic including http to switch over to the frame relay line. If the frame relay line goes down they would like all traffic to switch over and use the ADSL line.

I tried it using policy based routing, but that does not seem to work. I will post the configuration used as soon as I can, but feel free to post your ideas on how to achieve this.

[pkhatri]

Hi David,

PBR can be used to do this - use an extended ACL to match on HTTP packets.

For example, say that the WAN address on the far-end of the ADSL link is 192.168.1.1 and the WAN address on the far-end of the FR link is 172.16.1.1. Then you could do the following:

access-list 101 permit tcp any eq www any

access-list 101 permit tcp any any eq www

!

route-map PBR permit 10

match ip address 101

set ip next-hop 192.168.1.1

!

ip route 0.0.0.0 0.0.0.0 172.16.1.1

ip route 0.0.0.0 0.0.0.0 192.168.1.1 200

!

And on your LAN-facing interface:

int eth0/1

ip policy route-map PBR

Here's how this would work:

When both ADSL and FR links are up:

- http traffic will match the PBR route-map and will be routed to 192.168.1.1

- all other traffic will not match the PBR route-map and will be default-routed to 172.16.1.1 (since that default has a better administrative distance)

When ADSL is down and FR is up:

- the PBR next-hop will be down which means that all traffic will be routed via default means i.e over the FR link to 172.16.1.1

When FR is down and ADSL is up:

- http traffic will match the PBR route-map and will be routed to 192.168.1.1

- all other traffic will not match the PBR route-map and will be default-routed to 192.168.1.1 (the static default to 172.16.1.1 will be down since the FR interface is down)

Cheers,

Paresh.

[pkhatri]

Just one more thing, David.

If you find that the static defaults are not going down when the interface goes down, change them to point to the interface and not the IP address.

Paresh,