[168432] in North American Network Operators' Group
Re: Route Server Filters at IXPs and 4-byte ASNs
daemon@ATHENA.MIT.EDU (Sebastian Spies)
Sat Jan 25 10:48:51 2014
Date: Sat, 25 Jan 2014 16:48:32 +0100
From: Sebastian Spies <s+Mailinglisten.nanog@sloc.de>
To: nanog@nanog.org
In-Reply-To: <CAAYzVeE2K6WUh5X+gYAR6381v-wWPu2On_6GXGJBuZMdcoq0Ng@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Am 25.01.2014 16:38, schrieb Bryan Socha:
> Re-reading, I was thinking of someone connecting to an IXP, not a new
> IXP needing a 2Byte. This is an interesting situation and you are
> correct, my comment was off topic.
Sorry for not mentioning the beef: Extended Communities effectively
leave 6 bytes to the user. So, it is not possible, that a 4-byte-ASN IXP
encodes its own 4-byte-ASN and a 4-byte-ASN customer in one extended
community string. This is needed, as the IXP RS usually interpret their
own ASN and a peer ASN as: "Send this prefix out to the peer ASN".
To make things worse: even if the IXPs ASN is 2-byte, I would assume,
that RS implementors chose to interpret extended community strings as
always being in the format 4-byte:2-byte (see RFC5668).
Best regards,
Sebastian
