Re: Noisy prefixes in BGP

[Brian Knight via NANOG <nanog () nanog org>]

On 2025-02-09 07:43, James Bensley wrote:

> * There are no knobs in existing BGP implementations to detect and 
> limit this behaviour in anyway.

100% agreed. Looked into this a couple weeks ago on our $VENDOR_C gear, 
and we saw the prefixes Romain mentioned as well as many others in 
Geoff's report. I coded a CLI poller / screen-scraper to compare the 
different versions of the BGP table, in accordance with this tech 
article[1]. Seems to be as good as one can get with vanilla XR.

When looking at a specific prefix in the table, there is also a 
timestamp for the last update. It's helpful, but doesn't give a sense 
for how frequently it is updating.

Would be great to have logging / alerting if a locally originated prefix 
is updated more than once a second. Should also be easier to see high 
update load for those getting the updates downstream. A top N prefix 
frequency distribution based on short time windows (1-15 min) would have 
saved me work.

-Brian

[1] 
https://community.cisco.com/t5/service-providers-knowledge-base/bgp-churn-identification-on-ios-xr-asr9000-use-case/ta-p/4280504