From: Darryl Munro (Darryl.Munro@xxxxxxxxxxxxxxxxxx)
Date: Mon Aug 05 2002 - 05:28:57 GMT-3
Hi Larry,
I haven't tried this but you could give this a go.
Use a route-map with the set ip next-hop command as per the following
snippet from:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_c
/ipcprt2/1cdbgp.htm#xtocid27.
You would obviously have to have an IGP route to the hop you were after, it
is was a totally different AS then it seems strange that you would have any
connectivity to it other than through the AS that you already had a peer
with. Or do you have some other physical route\layer to get there, like a
backdoor route or something.
Disabling Next-Hop Processing Using a Route Map
To override the inbound next hop setting for BGP routes and specify that the
next hop of the matching routes is to be the IP address of the remote peer,
or to set the peering address of the local router to be the next hop of the
matching routes, use the neighbor next-hop-self command.
To configure the neighbor peering address to be used for the next hop
address, use the set ip next-hop command, beginning in route map
configuration mode:
Command Purpose
Router(config-route-map)#set ip
next-hop ip-address
[...ip-address] [peer-address]
In an inbound route map of a BGP peer, sets the next hop of the matching
routes to be the neighbor peering address, overriding any third-party next
hops and allowing the same route map to be applied to multiple BGP peers to
override third-party next hops.
With an outbound route map of a BGP peer, sets the next hop of the received
address to the peering address of the local router, disabling the next hop
calculation.
-----Original Message-----
From: Larry Roberts
To: Jason Sinclair; 'Dennis Laganiere'; ccielab@groupstudy.com;
cisco@groupstudy.com
Sent: 5/08/02 15:44
Subject: Re: What the heck is BGP Next Hop Propagation?
Group,
As a sidenote to this. Is there anyway to modify who the receiving BGP
router thinks is the advertising BGP router for a BGP route? I don't
mean
changing the next-hop, that doesn't work. I need to be able to modify
the
advertising router without peering to that router? For example:
BGP routing table entry for 150.50.1.0/24, version 0
Paths: (1 available, no best path)
Not advertised to any peer
69 65006
135.6.3.3 (metric 129) from 135.6.4.4 (135.6.4.4) <---- This is what
I
what to modify, I what to set it to 135.6.3.3 without peering directly
to
that router.
Origin IGP, localpref 100, valid, internal, not synchronized
Thanks,
Larry Roberts
CCIE #7886 (R&S / Security)
----- Original Message -----
From: "Jason Sinclair" <sinclairj@powertel.com.au>
To: "'Dennis Laganiere'" <Dennis@laganiere.net>;
<ccielab@groupstudy.com>;
<cisco@groupstudy.com>
Sent: Sunday, August 04, 2002 7:26 PM
Subject: RE: What the heck is BGP Next Hop Propagation?
> Dennis,
>
> This link explains it:
>
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft
/120
> limit/120st/120st16/st_bgpnh.htm
>
> This feature allows you to modify the next-hop attribute when
configuring
> route-reflectors and also allows you to send next-hop info to eBGP
peers
> that is not modified as per the normal rules of next hop changes when
> sending an advertisement to an eBGP neighbour. To sum it up the rules
of
BGP
> state that if a route is learned via iBGP then next hop info does not
change
> and we can use the bgp next-hop self statement to modify this. With
eBGP
> peers, the next hop info is modified at each eBGP router (in each AS)
so
> that the next hop appears as the advertising router. To modify this
you
can
> use the info in the attached link.
>
> Please let me know if this clarifies this, or if you would like
further
> explanation.
>
> 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: Dennis Laganiere [mailto:Dennis@laganiere.net]
> Sent: Tuesday, 6 August 2002 09:27
> To: ccielab@groupstudy.com; cisco@groupstudy.com
> Subject: What the heck is BGP Next Hop Propagation?
>
> In a semi-random CCO search I came across "BGP Next Hop Propagation",
but
> reading over the few links I've found isn't enough for me to figure it
out.
> I've looked through several BGP books and found nothing. I also tried
an
> archive search without results. Anybody seen this before? (I've got
to
> find
> a new hobby... :-)
>
> --- Dennis
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:48:16 GMT-3