nanog mailing list archives
Re: Long BGP AS paths
From: Tim Evens <tim () snas io>
Date: Mon, 02 Oct 2017 10:31:53 -0700
Yikes, my bad. In the CSV file it didn't seem so large. I setup a dashboard where you can browse the longest as paths for the selected time period. check out demo-rv.snas.io:3000/dashboard/db/top-as-paths?orgId=2 [3]. Change the time range to see those longer paths. They are no longer current in the last hour since cogent filtered them. --Tim On 01.10.2017 14:29, Tim Evens wrote:
The outliers are >100. Based on several peering points, <= 60 should be fine. See attached CSV file that shows the top 120 distinct AS Paths seen for the past month. Looks like 55644 likes to prepend a lot which is pushing the length above 50. --Tim On 01.10.2017 09:16, marcel.duregards--- via NANOG wrote: What would be a recommended value for a maximum as-path filter ? 50 ? On the DFZ I've only 11 prefixes longer than 30 as-path, so for safety I would also assume 50 as a max is well enough. Any advice ? Regards, - Marcel On 01.10.2017 00:29, William Herrin wrote: 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 [1] [1] Quagga: ip as-path access-list maxas-limit50 deny
^([{},0-9]+ ){50} ip as-path access-list maxas-limit50 permit .* Regards, Bill Herrin . Links: ------ [1] https://kb.juniper.net/InfoCenter/index?page=content&id=KB29321 [2] Links: ------ [1] https://kb.juniper.net/InfoCenter/index?page=content&id=KB29321 [2] https://kb.juniper.net/InfoCenter/index?page=content&amp;id=KB29321 [3] demo-rv.snas.io:3000/dashboard/db/top-as-paths?orgId=2
Current thread:
- Re: Long BGP AS paths marcel.duregards--- via NANOG (Oct 01)
- Re: Long BGP AS paths Tim Evens (Oct 01)
- Re: Long BGP AS paths Tim Evens (Oct 01)
- Re: Long BGP AS paths Tim Evens (Oct 02)
- <Possible follow-ups>
- Re: Long BGP AS paths Mark Price (Oct 01)
- Re: Long BGP AS paths sthaug (Oct 01)
- Re: Long BGP AS paths Jon Lewis (Oct 01)
- Re: Long BGP AS paths sthaug (Oct 01)
- Re: Long BGP AS paths William Herrin (Oct 01)
- Re: Long BGP AS paths Randy Bush (Oct 01)
- Re: Long BGP AS paths Scott Weeks (Oct 01)
- Re: Long BGP AS paths Tim Evens (Oct 01)