On Thu, Jun 30, 2016 at 04:28:00PM +0300, Javor Kliachev wrote: > Hello, > > We use BIRD as route server with the well-known "BGP Community policy based > filtering" as in most of all other IXP with the following type: > ... > But recently we came across the following case: > > A member of our IXP is sending his prefixes with attached a huge count of > BGP communities ( ~ 750 pcs ) > > Each of the attached community has following type: 0:ASN ( peer-as ). > > We see that BIRD accepts these prefixes from member but it return the > following error notification: > > 2016-06-30 10:06:59 <ERR> R0_248: Attribute list too long, skipping
Hi By RFC 4271, BGP message is limited to 4 kB of length. BIRD internally limits attribute part of a transmitted message to 2 kB. This is equivalent of 1024 (4 kB) or 512 (2 kB) communities. You could replace constants 3072 [1] and 2048 [2] with say 3840 and 3584, that would allow 3.5 kB of attributes (~ 900 communities). [1] proto/bgp/packets.c:372 and proto/bgp/packets.c:465 [2] proto/bgp/packets.c:385 and proto/bgp/packets.c:481 Or, as these communities are destinated for your IXP, you could simply strip 0:* and IPX_AS:* communities before prefixes are forwarded to your clients. This is probably a good idea anyways as having too large attribute list may cause problems later. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
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