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cwachs
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ECMP / Local Pref not working in ROS 7

Mon Jan 30, 2023 1:50 am

I am chasing down a routing issue on a ROS 7.6 router (also is happening in 7.7). We have iBGP inserting routes from multiple paths. We use route filters to add a local-pref number to the incoming routes based on the BGP peer. In the Route table, it is not using the local-pref value, it is inserting the route as ECMP and basically round robining the traffic.

What I expect the router to do is honor the higher local-pref numbers. It does that in our ROS 6 routers. Why is it not honoring this in ROS 7.6? Here is an example of our routing table where you can see the local pref is properly set but both routes are active in the table. The primary route has a local-pref of 100 and the backup path we set a local-pref of 50 (sorry, I cut off the table labels).
Screenshot 2023-01-29 at 1.36.09 PM.png
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cwachs
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Re: ECMP / Local Pref not working in ROS 7

Mon Jan 30, 2023 4:38 am

Was able to get routes working correctly but I had to add a distance filter to the route filter:
else { set bgp-local-pref 50; set distance +1; accept; }
Just having a local-pref for a iBGP route would not give it a preference. Changing the distance on one path to 201 did - but local-pref works fine in ROS6 on this same hardware (CCR1036).

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