From: damien (damien@xxxxxxxxxxx)
Date: Tue Oct 03 2000 - 15:19:09 GMT-3
This may not be the answer but I did notice when the primary route was
re-enabled, it appeared almost immediately in the the BGP Table...
......whilst the backup route took a long time to vanish.............
The same happened vice versa, when I shut down the primary route..........it
took what seemed like an eternity for the backup route to appear in the
table......
bare in mind this is a small test network.....4 Routers with only 10 or so
prefixes...so convergence should not be an issue...
----- Original Message -----
From: "Mark Lewis" <markl11@hotmail.com>
To: <m.bell@wilcom.com>; <ccielab@groupstudy.com>
Sent: Tuesday, October 03, 2000 11:38 AM
Subject: RE: Conditional BGP Advertisements
>
> Yup, the 'backup' route has to be also present in the bgp table before it
> can be advertised in the absence of the primary route.
>
> To confirm that everything is working as planned, use the 'sh ip bgp
neigh'
> command and look for the part of the output which shows the status of the
> advertise map.
>
> Hope that helps,
>
> Mark
>
>
> >From: "Bell, Mark (Houston)" <m.bell@wilcom.com>
> >Reply-To: "Bell, Mark (Houston)" <m.bell@wilcom.com>
> >To: "CCIE Study Group (E-mail)" <ccielab@groupstudy.com>
> >Subject: RE: Conditional BGP Advertisements
> >Date: Mon, 2 Oct 2000 21:53:11 -0500
> >
> >I have attempted to configure a conditional advertisement in my network
> >using the following config:
> >
> >router bgp 3
> > no synchronization
> > neighbor 10.10.1.3 remote-as 2
> > neighbor 10.10.1.3 advertise-map BACKUP non-exist-map BACKUP2
> > neighbor 10.10.1.5 remote-as 3
> > neighbor 10.10.1.5 route-reflector-client
> > neighbor 10.20.1.2 remote-as 3
> > neighbor 10.20.1.2 route-reflector-client
> >!
> >ip classless
> >no ip http server
> >ip as-path access-list 1 permit _\(65005\)$
> >!
> >access-list 1 permit 6.0.0.0
> >access-list 2 permit 11.1.0.0
> >route-map BACKUP permit 10
> > match ip address 1
> >!
> >route-map ASPATH permit 10
> > match as-path 1
> > set local-preference 500
> >!
> >route-map BACKUP2 permit 10
> > match ip address 2
> >
> >When I go to the router 10.10.1.5 that advertises 11.1.0.0/16 and shut
down
> >it's link to this router, 11.1.0.0/16 disappears from the BGP table as
> >expected. If I understand conditional advertisements correctly, the
router
> >should begin advertising 6.0.0.0/8 to 10.10.1.3 because 11.1.0.0/16 is
> >gone.
> >The problem is, 6.0.0.0/8 never shows up anywhere.
> >
> >Does the backup route have to be present in the BGP table prior to the
> >monitored route disappearing or will it be injected into the BGP table
only
> >when necessary? Are there any restrictions as to whether the monitored
or
> >backup route must be learned via iBGP or eBGP?
> >
> >-----Original Message-----
> >From: Stylen [mailto:globalfx@netropolis.net]
> >Sent: Friday, September 29, 2000 21:26
> >To: ccielab@groupstudy.com
> >Subject: Re: Conditional BGP Advertisements
> >
> >
> >Yes, BGP will look for the route in its routing table, if it goes away,
> >then
> >the routes in the advertise list will be advertised via eBGP. this is
used
> >for backing up a link, i.e. if you have two routers connected to to a
> >external network. You might only want one of them advertising a specific
> >route, perhaps because of location, but if the link between that router
and
> >the external network goes down, then the second router will begin
> >advertising the route for redundancy. if you have the second router watch
> >for the link between the first router and the external network in its
> >routing table, when the route goes dissappears, then it knows to
advertise
> >the route designated by advertise-map.
> >
> > Internet
> > | |
> > | |204.0.0.4/30
> > R1------R2
> > |
> > |
> > 204.2.3.0/24
> >the 204.0.0.5 route will be in R1's routing table, via a IGP. when the
link
> >between R2 and the internet goes down, then the 204.0.0.5 route will
> >dissappear from the routing table in R1 then R1 will advertise the route
to
> >204.2.3.0/24 to the internet. When the 204.0.0.4/30 route comes back up,
R1
> >will stop advertising 204.2.3.0/24, and R2 will take over.
> >
> >Richard Foltz, CCNP, CCNP-Voice, CCDP, MCSE+I, Network+, A+
> >Technical Solutions Consultant
> >Sprint ENS
> >
> >
> >
> >-----Original Message-----
> >From: abdul_rahim@ccsi.canon.com <abdul_rahim@ccsi.canon.com>
> >To: ccielab@groupstudy.com <ccielab@groupstudy.com>
> >Date: Friday, September 29, 2000 7:58 PM
> >Subject: Conditional BGP Advertisements
> >
> >
> > >The following statement as described on cisco in BGP routing process
> > >neighbor a.b.c.d advertise-map <route-map 1> no-exist-map <route-map 2>
> > >
> > >
> > >Advertises the routes specified in route-map1 when it finds that the
> >routes
> > >specified in route-map 2 does not exists any more in the BGP table
> > >And they call it as Conditional Advertisement
> > >
> > >My question is that the routes in route-map1 ,do they have to be
present
> >in
> > >the BGP table,
> > >I am not getting the point at all
> > >
> > >Can some body explain it to all of the group in a bit detail or
redirect
> >to
> > >a certain URL ,I do have the URL on cisco sit
> > >http://cisco.com/warp/public/459/34.html
> > >
> > >Any feedbacks would be highly appreciated
> > >Thanks
> > >Abdul
> > >
> > >
> > >
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