From b6bf284a905412cfe107b4967e55649e6194187e Mon Sep 17 00:00:00 2001 From: Ondrej Zajicek Date: Sun, 26 Oct 2008 22:59:21 +0100 Subject: Bugfixes in MULIT_EXIT_DISC attribute handling. - Old MED handling was completely different from behavior specified in RFCs - for example they havn't been propagated to neighboring areas. - Update tie-breaking according to RFC 4271. - Change default value for 'default bgp_med' configuration option according to RFC 4271. --- doc/bird.sgml | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) (limited to 'doc') diff --git a/doc/bird.sgml b/doc/bird.sgml index 5ee9562..8fa55f8 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -784,7 +784,7 @@ for each neighbor using the following configuration parameters: default bgp_med Value of the Multiple Exit Discriminator to be used during route selection when the MED attribute - is missing. Default: infinite. + is missing. Default: 0. default bgp_local_pref Value of the Local Preference to be used during route selection when the Local Preference attribute @@ -806,10 +806,16 @@ with `int The Multiple Exit Discriminator of the route - is an optional attribute which is often used within the local AS to - reflect interior distances to various boundary routers. See the route selection - rules above for exact semantics. + int The Multiple Exit Discriminator of the route + is an optional attribute which is used on on external (inter-AS) links to + convey to an adjacent AS the optimal entry point into the local AS. + The received attribute may be also propagated over internal BGP links + (and this is default behavior). The attribute value is zeroed when a route + is exported from a routing table to a BGP instance to ensure that the attribute + received from a neighboring AS is not propagated to other neighboring ASes. + A new value might be set in the export filter of a BGP instance. + See RFC 4451 + for further discussion of BGP MED attribute. enum Origin of the route: either