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Monday, January 10, 2011

How can we configure a router (in this case a 6509) to monitor a the 3rd party network (subnet or interface) and advertise a route into our network ?

Our EIGRP network will soon be connected to a 3rd party network which we have no control over. The 3rd Party are refusing to take part in any dynamic routing but have hundreds of non-contigous subnets which we must route using static routes. To compound things further we'll have two routes into the 3rd party network (a primary and a secondary) for resilience. Ideally the connectivity should switch between the two links without any manual reconfiguration.

Is there a way that we can configure a router (in this case a 6509) to monitor a the 3rd party network (subnet or interface) and advertise a route into our network as long as that interface or subnet is up? If our network looses contact with the 3rd party network or interface then our 6509 stops advertising that route into the network.

Tips:

What you can do is configure the route and associate it with a IP SLA. Just for example : Say you intend to configure a route as

ip route 192.168.1.0 255.255.255.0 172.168.1.1

You can track the reachability of the ip address 172.168.1.1 provided that ICMP is allowed for this IP

ip sla monitor 10
type echo protocol ipIcmpEcho 172.168.1.1 source-ipaddr src-ip-addr --- this could be your own interface ip

track 10 rtr 10 reachability

ip route 192.168.1.0 255.255.255.0 172.168.1.1 track 10

What will happen is that your router will continusly ping the next hop ip addr (172.168.1.1) and if the ping fails then the static route will be removed from the routing table. Only those static routes are redistributed those are present in the routing table. So the redistributed route in the EIGRP would be removed when the SLA fails.

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.

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