From: Mark Lewis (markl11@xxxxxxxxxxx)
Date: Mon Feb 04 2002 - 13:50:26 GMT-3
Yep, we were talking about eBGP, but the original post showed a bit of
confusion as to BGP split-horizon, hence my explanation.
If memory serves me right, RFC 1771 states that routes received in the
Adj-RIB-In have the policies in the Policy Information Base (PIB) applied,
and are then placed in the Adj-RIB-Out for advertisement to neighbors. No
mention of an AS check outbound to external neighbors (unless explicitly
configured in the PIB by way of local config, or ORF is in use).
Rgds,
Mark
>From: John Neiberger <neiby@ureach.com>
>Reply-To: <neiby@ureach.com>
>To: "Mark Lewis" <markl11@hotmail.com>, ccielab@groupstudy.com
>Subject: Re: Re: Junos BGP routes update
>Date: Mon, 4 Feb 2002 10:57:40 -0500
>
>That statement is certainly true but I thought we were
>discussing eBGP, not iBGP. I thought he was referring to a
>scenario where an eBGP peer receives an update from another
>eBGP peer that includes its own ASN.
>
>Let's say AS1 has routers A and B, both of which are connected
>to AS2, routers C and D. Both A and B advertise their prefices
>to C and D who in turn trade updates. Then C will advertise
>back to AS1 the routes it learned from D. The receiving router
>in AS1 will see its own ASN in the AS-PATH and drop the update.
>
>I believe that the original poster thought that AS2 wouldn't
>even transmit an update to AS1 that had AS1 in the AS-PATH.
>I'm fairly sure that it is up to the receiving router to check
>the AS-PATH for its own ASN, not the advertising router.
>
>Regards,
>John
>
>
This archive was generated by hypermail 2.1.4 : Thu Jun 20 2002 - 13:46:11 GMT-3