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Change EIGRP Metric for received routes

Bill19795_2
Level 1
Level 1

I have the following setup. Router1 is connected to MPLS provider1. We are doing BGP to the provider and EIGRP internally. Switch1 is a layer 3 switch and is doing EIGRP STUB routing. I am receiving all of the routes from provider1 to Switch1 from EIGRP. Switch1 is also the default gateway for the location.

I am now in the process of implementing a “backup” network to a remote datacenter that is hosting our primary application. Let’s call this Router2 connected to MPLS provider2. This setup will be a managed connecting from the provider and I will not have access to the equipment. They will also send routes to Switch1 using EIGRP. I will only use provider 2 in the event the route to one location is down, say network 10.10.10.X. On Switch1 my preferred route should always be provider1, in the event that the route to network 10.10.10.X is lost from provider1 I should use provider2.

I could get this to work easily if I had control of Router2 but I do not. I am also very limited in what I can require them to use to send the routes. They basically want to send it as the default and leave it to me to manipulate the route.

So is there a way I can manipulate the metric I receive from router2 within my switch1?

15 Replies 15

cadet alain
VIP Alumni
VIP Alumni

Hi,

you could use an offset-list to increase the metric of received routes.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800c2d96.shtml#modifycompositemetric

Regards.

Alain.

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I looked at this but wouldn’t I need to apply the offset list on Router2 to manipulate Switch1.

Hi,

in the doc it was applied outbound but it can also be applied inbound which would be your case.

Regards.

Alain.

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So if I apply it inbound on Switch1 would it also modify the same route I receive from Router1? Does the ACL match the neighbor I receive the route from or the actual route.

Hi,

you can specify on which interface it is received at the end of the offset-list command.

eg: offset-list 10 in 100 fa0/0

Regards.

Alain

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So I can create an ACL to match network 10.10.10.X then apply it inbound to EIGRP but only change the metric if it matches the interface that Router2 is connected to? So would it look something like this:

ip access-list standard test

permit 10.10.10.0 0.0.0.255

deny   any

!

router eigrp 110

offset-list test in 100 FastEthernet0/10

This would only modify the metric of routes learned from Router2 which is connected to Faste0/10 not the same router that is learned from Router1 connected to Faste 0/9 ?

Yes it is exactly what it would do but you'll have to use the right offset value to get the desired result.

Regards.

Alain.

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Wouldn't I just need to increase the metric to a higher value than what I am getting from Router1.

Also how does it know to just apply it to routes received from interface faste0/10? I didn't think that information was carried anywhere in the EIGRP packet. How does it know to only apply it to routes learned from that specific interface?

Hi,

That's what the feature does: increase the metric of the route without for a specific route.

It know it comes on f0/1 because you told so by specifying the interface at the end of the command.

Regards.

Alain.

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This is not working as expected. I set this up in my lab and I am getting the following results. When I apply the offset list to EIGRP AS without using the interface command it modifies the metric. When I apply the interface command using the interface the router is connected to on the switch it does not modify anything for either route. When I apply the interface command using the VLAN as the interface it works as expected. This is why I was asking on how EIGRP knew what interface it was using. To it the routes are not being learned on the physical interface but on the SVI interface. Is there anyway to accomplish this?

Hi,

The switch can only do routing on a routed port or an SVI which is your case.

You said it was working this way, so why don't you want to use the SVI?

You could also change the delay or bandwidth of the SVI but it will be for all routes not a specific one.

As of right now I don't see any other way of doing this on the switch.

Regards.

Alain.

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If I apply it to the SVI it applys the offset to both routes from Router1 and Router2, I only want to change the routes from Router2.

Hi,

post your network diagram.

Regards.

Alain.

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So the IP's are differnt in my lab but the 10.10.1.X network is my internal LAN Network. 200.1.1.X network is the network segment that will be advertised by both Router1 and Router2. Right If I look at Switch1 I have the following output.

EIGRP-IPv4 Topology Table for AS(10)/ID(10.10.1.10)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 200.1.1.0/24, 2 successors, FD is 130816
        via 10.10.1.11 (130816/128256), Vlan10
        via 10.10.1.12 (130816/128256), Vlan10
P 10.10.1.0/24, 1 successors, FD is 2816
        via Connected, Vlan10

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