Hi Shunwan, Yes, that is a curious thing ... it seems peculiar and specific to AS 3356. I have started a discussion on NANOG about 3356:666, 3356:9999, etc. Please take a look: https://mailman.nanog.org/pipermail/nanog/2021-August/thread.html#214447
Only AS 3356 may be an outlier. Most other AS operators use ASN:666 or WKC 65535:666 for Blackhole Community: https://www.google.com/search?q=BGP+community+%3A666&rlz=1C1GCEV_enUS847US847&oq=BGP+community+%3A666&aqs=chrome..69i57j69i64.9798j1j15&sourceid=chrome&ie=UTF-8&safe=active&ssui=on Also, we'll check -- on slide 12 of my GROW presentation -- out of the roughly 265K count of unique {Prefix, AS Path, RC = Any:666}, how many are with 3356:666. I will let you know. Sriram ________________________________________ From: GROW <[email protected]> on behalf of Zhuangshunwan <[email protected]> Sent: Tuesday, August 3, 2021 10:37 PM To: Sriram, Kotikalapudi (Fed); GROW WG Cc: IDR Subject: Re: [GROW] some questions from {RC, LC, EC} analysis presentation in GROW Hi Sriram, The community attribute example 3356:666 on page 10 may not match the actual function. " Example: AS path = 25160 3356 12956 6147 and RC = 3356:666 This means that the client is at AS 6147 (origin AS) and AS 3356 is the RTBH provider AS Distance to RTBH provider = 2 Propagation (#hops): The Blackhole Community propagated 3 hops in this case (AS 6147 to AS 25160) " According to https://onestep.net/communities/as3356/ ... -------------------------------------------------------- prefix type communities -------------------------------------------------------- 3356:123 - Customer route 3356:666 - Peer route -------------------------------------------------------- ... -------------------------------------------------------- customer traffic engineering communities - Blackhole -------------------------------------------------------- 3356:9999 - blackhole (discard) traffic Traffic destined for any prefixes tagged with this community will be discarded at ingress to the Level 3 network. The prefix must be one permitted by the customer's existing ingress BGP filter. For some router vendors the peering must be changed to an eBGP multihop session on the Level 3 side of the connection. ... Regards, Shunwan _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
