Failover link 7206

[dgj]

We have a Cisco 7206 and a 100Mbps link to another site.

However, I'd like to be able to link a second 10Mbps link to this site in the following way:

Fast0/0 100Mbps link to Site B

Eth4/0 10Mbps link to Site B - only when primary link fails.

I don't need to load balance on the links as utilisation is not an issue.

It's just the failover situation i need to address.

(currently on c7200-ik9o3s-mz.122-8.T5 IOS)

Any help much app.

G

[sstudsdahl]

If you are using a routing protocol such as EIRGP or OSPF and are running IP, you shouldn't have any problems doing this. The 100Mbps link will be prefered over the 10Mbps. If the 100Mbps link goes down, the routing protocol will lose the information learned via teh 100Mbps link and should then place the routes learned via the 10Mbps link in the forwarding table. You will still see traffic going across the 10Mbps link, but this should mostly be routing protocol traffic and any traffic that is destined to the 10Mbps subnet (your router interfaces). If you have other protocols, such as IPX running across the link, it will end up load balancing across both links.

[dgj]

the 7206 is the default router for this site

so can I specify ip address as 172.x.y.1 on both interfaces?

it's going to be difficult to test this in a live environment!!!!

[jamey]

Both links will require unique subnets.

e.g.

100Mbps link:

(7206)172.16.1.1/30 - 172.16.1.2/30(other router)

10Mbps link:

(7206)172.16.1.5/30 - 172.16.1.6/30(other router)

As the other poster stated, if you are using a dynamic routing protocol, you should be ok.

If you are using static routes you could use floating static routes.

e.g. you could do this on the remote router (if you had the IP subnet scheme above)

ip route 0.0.0.0 0.0.0.0 172.16.1.1

ip route 0.0.0.0 0.0.0.0 172.16.1.5 200

and then on the 7206 (if 192.168.1.0/24 was the subnet hanging off the remote router i.e. the LAN subnet)

ip route 192.168.1.0 255.255.255.0 172.16.1.2

ip route 192.168.1.0 255.255.255.0 172.16.1.6 200

Hope this helps ya.

[#5]

Are 100m link and 10m link connected to 2 different routers or the same router on the other side? If 2 different routers, you may implement HSRP between these two routers.

[dgj]

I probably haven't explained properly!

There aren't any routers on the other end as the links are IR and wireless(microwave) and the default gateway for the network on the other end of the link(s) is the 7206.

If I have to I probably would be able to put another router on the other end (2621?)

Can i use HSRP if there's nothing on the other end?

If so, how?

Many Thanks to all!

[sstudsdahl · Accepted solution]

With the IR/microwave connection going directly into the remote LAN, you will need a second router in order to place the 10Mb link into a backup mode. The second router is required in order to use HSRP as IOS will not allow you to put an IP address on an interface for a subnet that already has been configured on a different interface.

You can place the second router next to the 7206 to service the backup link and use HSRP with the 7206 (100Mb link) acting as the active router. The caveat to this is the routers that are setup for HSRP will need to be able to detect when the IR/microwave link goes down. If the router interface stays up even though the IR/microwave link is down, HSRP will not work.

By deploying the second router between the IR/microwave links and the remote LAN, you can use either a routing protocol or floating static routes to place the 10Mb link into a backup role. Doing this will require three interfaces in the router. One for the IR link, one for the microwave link, and one for the remote LAN connection. These interfaces can be either physical or logical subinterfaces. In order to use logical interfaces, you would need to establish an 802.1q or ISL trunk to a LAN switch. You would need to define a separate VLAN for the IR link, a VLAN for the micrwave link, and a VLAN for the remote LAN along with the corresponding interfaces on the second, remote router.