EIGRP - preferred route in E-Metro

[denis.ivitchev]

We have 2 data centers - R1 and R2 and multiple remote offices all connected via E-Metro mesh. We want R3 office to go via R2 data center to offload R1. Any pointers how to make R3 to chose R2 as preferred peer? Thank you.

[paul driver]

Hello

You could influence the path various ways:

Increasing the interface delay on R3- R1 or he eigrp admin distance so primary path would take R2

You could also summarize a particular network so again the most specific route within that summary is chosen via the alternative path

You could introduce a offset-list for partiticular network to take R3-R2 path 

[Deepak Kumar]

Hi,

You have multiple options for setting a preferred route by Influencing EIGRP Metrics. 

1. Change the Interface Delay Parameter. You can increase the delay between R3 and R1 interface so it will choose the R3 to R2 interface as the best route. 

2. Use an offset-list: You can use the offset list for Influencing EIGRP Metrics. Keep in mind it will only increase the metric (delay K value).

3. Change the AD value between R3 and R1 EIGRP neighbor. 

Here is a TAC document with all details. 

https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13673-14.html

Regards,

Deepak Kumar

[denis.ivitchev]

Thank you guys for your responses but I don't think any proposed suggestion would work for us. I should've specified in the original post but our setup is the full mesh so there's only one interface on each router which means that modifying metrics would affect route advertisements from both R1 and R2.

[paul driver]

Hello

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@denis.ivitchev wrote:

Thank you guys for your responses but I don't think any proposed suggestion would work for us. I should've specified in the original post but our setup is the full mesh so there's only one interface on each router which means that modifying metrics would affect route advertisements from both R1 and R2.

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You could still perform path manipulation based in admin distance as you change the admin distance based on the eigrp routers adverting rid which would make that particular neighbors routes be seen as a less preferred for all or specific internal route prefixes, For any external routes then you would need to advertise a less preferred metric.

[Deepak Kumar]

Hi,

Change configuration on R3 as below:

Router eigrp 1

distance 91 172.30.0.1 0.0.0.0

This increases the AD value from 90 to 91 which are learning from the neighbor 172.30.0.1. So you will find routes in the routing table with are learned from the neighbor 172.30.0.1 because of lower ad value.

Regards,

Deepak Kumar