RE: BGP - Tags

From: Andrew Lissitz \(alissitz\) (alissitz@cisco.com)
Date: Tue Oct 11 2005 - 19:20:48 GMT-3


Thanks! I started to read this earlier ... (snoring was heard) ... will
save the rest till evening ... maybe ... Actually ... it is not that
bad. I did not realize that this was defined so long ago ... thanks for
sending.

________________________________

From: kgannon@gmail.com [mailto:kgannon@gmail.com] On Behalf Of kevin
gannon
Sent: Tuesday, October 11, 2005 2:08 PM
To: Andrew Lissitz (alissitz)
Cc: Luis Rueda; Bob Sinclair; C&S GroupStudy; Cisco certification
Subject: Re: BGP - Tags

In case you have trouble sleeping you can also look into the use
of automatic-tags when doing OSPF to BGP redistribution see
section 4. of the following RFC:

http://www.faqs.org/rfcs/rfc1364.html

Regards
Kevin

On 10/11/05, Andrew Lissitz (alissitz) <alissitz@cisco.com> wrote:

        Hello Luis and group,

        Luis; I added your request to this email thread so as to keep
this
        thread in sync. You asked for the show ip bgp output
10.131.96.0. Bob
        mentioned that this was normal, is this what you see as well?

        If anyone has any comments to my last email, I would greatly
appreciate
        it. Kindest regards,

        PE1#sh ip bgp 10.131.96.0
        BGP routing table entry for 10.131.96.0/24, version 17
        Paths: (2 available, best #2)
          Not advertised to any peer
          200
            10.131.63.226 (metric 116) from 10.131.63.255
(10.131.63.255)
              Origin IGP, metric 0, localpref 100, valid, internal
              Originator: 10.131.63.251, Cluster list: 10.131.63.255
          200
            10.131.31.242 (metric 106) from 10.131.31.255
(10.131.31.255)
              Origin IGP, metric 0, localpref 100, valid, internal, best

              Originator: 10.131.31.251, Cluster list: 10.131.31.255

        PE1#sho ver
        Cisco Internetwork Operating System Software
        IOS (tm) 3600 Software (C3640-P-M), Version 12.0(25)S, EARLY
DEPLOYMENT
        RELEASE SOFTWARE (fc1)

        ________________________________

        From: Andrew Lissitz (alissitz)
        Sent: Tuesday, October 11, 2005 11:06 AM
        To: 'Bob Sinclair'; C&S GroupStudy; Cisco certification
        Subject: RE: BGP - Tags

        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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