From: Mark Lewis (markl11@xxxxxxxxxxx)
Date: Tue Oct 03 2000 - 08:38:57 GMT-3
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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