BGP Attributes

[zillah2004]

In the semester 5 Cisco Companion book :

Table 8-2 the "Well-Known discretionary" type are three:

1- LOCAL_PREF

2- ATOMIC_AGGREGATE

3- AGGREGATOR

I had read an article on cisco site (I will post it when I found it),that the "Well-Known discretionary" type are two only, not three (like the book mentioned), which are :

1- LOCAL_PREF

2- ATOMIC_AGGREGATE

Which one is the accurate one ?

[stschmidt]

RFC 1771 defines these below as well-known discretionary attributes.

LOCAL_PREF (Type Code 5)

ATOMIC_AGGREGATE (Type Code 6)

http://www.rfc-archive.org/getrfc.php?rfc=1771

[zillah2004]

Does that mean the AGGREGATOR attribute has been added mistakely to "well-known discretionary" in the Cisco Book ?

[Harold Ritter]

The AGGREGATOR attribute is indeed defined as an optional transitive attribute by both RFC1771 and by draft-ietf-idr-bgp4 (http://www.ietf.org/internet-drafts/draft-ietf-idr-bgp4-26.txt). It seems like this was overlooked in the book.

Hope this helps,

[justin.white]

Here's a reference you'll want to bookmark:

http://www.iana.org/assignments/bgp-parameters

This is a definitive list of BGP message types, attributes, and error codes. For each of the attributes listed, there is a corresponding RFC (whether official or draft). Easiest way to find the document listed is to Google the file name as it's listed.

HTH,

JW