From: Jason Sinclair (sinclairj@powertel.com.au)
Date: Mon Feb 24 2003 - 21:14:35 GMT-3
Jerry,
Split-horizon with respect to IGP's also operates above layer 3. The command
to "turn off split-horizon" for BGP would be neighbour x
route-reflector-client. I think the original question was does split-horizon
come into play with BGP and the answer would be yes, however not in the same
way as it does with IGP's...........
Regards,
Jason Sinclair CCIE #9100
Manager, Network Control Centre
POWERTEL
55 Clarence Street,
SYDNEY NSW 2000
AUSTRALIA
office: + 61 2 8264 3820
mobile: + 61 416 105 858
email: sinclairj@powertel.com.au
-----Original Message-----
From: Jerry Haverkos [mailto:jhaverkos@columbus.rr.com]
Sent: Tuesday, 25 February 2003 09:21
To: Howard C. Berkowitz; ccielab@groupstudy.com
Subject: RE: split-horizon & BGP
Howard
I do not believe that the is a command to turn split-horizon on or off
available for BGP, especially not one that works at layer 3. My point is
that BGP does not run at the layer 2 or layer 3 or even layer 4 part of the
stack. It is an application that exchanges data via an established BGP TCP
session. It is an application to application (BGP peer to peer) decision not
to send routes back to a peer that it received the routes from.)
I do not believe that it has anything to do with the traditional idea that
split horizon does not allow updates, received over an interface, to be sent
back over that interface. ;)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Howard C. Berkowitz
Sent: Monday, February 24, 2003 3:13 PM
To: ccielab@groupstudy.com
Subject: RE: split-horizon & BGP
At 12:30 PM -0500 2/24/03, OhioHondo wrote:
>Since BGP runs as a higher layer protocol (on top of TCP) split horizon
does
>not apply.
Why do you think TCP would make a difference in loop detection?
BGP is not strictly a DV protocol. Its primary loop detection method
is examining incoming AS paths (i.e., path vectors) and rejecting
those that contain the local AS number.
There are additional methods, for iBGP using confederations and RR's,
to reduce/eliminate transient internal loops/oscillation, but these
are probably outside the CCIE scope.
It isn't completely clean, as BGP/PV is provably loop-free only when
additional policies are NOT used.
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>Pedro Eira
>Sent: Monday, February 24, 2003 10:36 AM
>To: ccielab@groupstudy.com
>Subject: split-horizon & BGP
>
>
>Hello, Would split-horizon have any effect on BGP?Should I follow the
>same rules for BGP as I do for other DV routing protocols when
>split-horizon is involved?
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