Long BGP AS paths

William Herrin bill at herrin.us
Sat Sep 30 22:29:36 CST 2017


To the chucklehead who started announcing a 2200+ byte AS path yesterday
around 18:27 EDT, I beg of you: STOP. You've triggered a bug in Quagga
that's present in all versions released in the last decade. Your
announcement causes routers based on Quagga to send a malformed update to
their neighbors, collapsing the entire BGP session. Every 30 seconds or so.

For everyone else: please consider filtering BGP announcements with
stupidly long AS paths. There's no need nor excuse for them to be present
in the DFZ and you could have saved me a painful Saturday.

Cisco:

router bgp XXX
 bgp maxas-limit 50


Juniper:
https://kb.juniper.net/InfoCenter/index?page=content&id=KB29321


Quagga:

ip as-path access-list maxas-limit50 deny ^([{},0-9]+ ){50}
ip as-path access-list maxas-limit50 permit .*


Regards,
Bill Herrin


-- 
William Herrin ................ herrin at dirtside.com  bill at herrin.us
Dirtside Systems ......... Web: <http://www.dirtside.com/>


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