RE: BGP - Tags

From: Andrew Lissitz \(alissitz\) (alissitz@cisco.com)
Date: Tue Oct 11 2005 - 12:05:36 GMT-3


You rock Bob! I guess I never noticed this in the past ... sometimes I
need to smell the roses. Does anyone know if this was always the case?

With this info now... can we do clever tricks with filtering just as if
we had set the tags ourselves? Sorry if this should be self explanatory
.... it seems convenient to have these tags put on auto-magically...

________________________________

From: Bob Sinclair [mailto:bob@bobsinclair.net]
Sent: Tuesday, October 11, 2005 10:58 AM
To: Andrew Lissitz (alissitz); C&S GroupStudy; Cisco certification
Subject: Re: BGP - Tags

Andrew,

This does appear to be normal behavior. I also see the AS number from
which this AS learned the prefix as a TAG.

HTH,

Bob Sinclair
CCIE #10427, CCSI 30427, CISSP
www.netmasterclass.net

        ----- Original Message -----
        From: Andrew Lissitz (alissitz) <mailto:alissitz@cisco.com>
        To: C&S GroupStudy <mailto:comserv@groupstudy.com> ; Cisco
certification <mailto:ccielab@groupstudy.com>
        Sent: Tuesday, October 11, 2005 10:00 AM
        Subject: BGP - Tags

        Hello Folk,

        In a lab I was doing I, there were multiple BGP AS#s. All the
BGP
        routers were speaking to each other. There were no problems
with
        routing or anything ... my question is related to some show
commands I
        saw. Here goes:

        PE1#show ip route 10.131.96.0
        Routing entry for 10.131.96.0/24
          Known via "bgp 100", distance 200, metric 0
          Tag 200, type internal
          Last update from 10.131.31.242 4d22h ago
          Routing Descriptor Blocks:
          * 10.131.31.242, from 10.131.31.255, 4d22h ago
              Route metric is 0, traffic share count is 1
              AS Hops 1, BGP network version 0
              Route tag 200

        @ the bottom of this you will see the tag 200. This was learned
from a
        bgp AS # 200. There was no tagging set (please do not ask for
configs)
        ... This is a MPLS lab / network ... I would not think that this
would
        make a difference ...

        Is this normal... BGP 'auto tagging' of routes learned from
different AS
        numbers?

        Kindest regards,

        Andrew



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