Large prefix lists/sets on IOS-XR

Jakob Heitz (jheitz) jheitz at
Fri Dec 9 18:12:41 UTC 2022


How big? How slow?
You can reply to me off or on list.

About 8 to 10 years ago, we had a large effort to improve this.
Now customers push many megabytes of prefix-sets several times a day and it works.
I have sent some questions internally to get a better answer.

Related, in 7.2.1, we added the as-set, which allows you to filter BGP routes by origin-as.
It is similar to as-path-set.
as-path-set is slow, using a linear lookup, but it is versatile, allowing ios-regex.
as-set can only use numbers and only for origin-as, but it is fast using a log(N) lookup.


-----Original Message-----
Date: Fri, 9 Dec 2022 00:02:52 +0100
From: Sander Steffann <sander at>


What is the best/most efficient/most convenient way to push large prefix lists or sets to an XR router for BGP prefix filtering? Pushing thousands of lines through the CLI seems foolish, I tried using the load command but it seems horribly slow. What am I missing? :)


for every complex problem, there?s a solution that is simple, neat, and wrong

More information about the NANOG mailing list