From: Richard Davidson (rich@myhomemail.net)
Date: Sun Jan 04 2004 - 20:20:29 GMT-3
your question:
Q.
> When we redistribute from BGP to an IGP protocol, is
> it the routes from the routing
> table or from the BGP table that must be taken into
> consideration?
A. When you redistribute from bgp, the bgp routes in
the routing table are redistributed. If it is in the
bgp table but not in the routing table the route is
not redistributed.
Rich
--- ccie8966 <ccie8966@wanadoo.fr> wrote:
> Hi,
>
> in this lab topology (not a "real-life" one), we
> connected
> two routers back-to-back. An OSPF adjacency is full
> between R1
> and R2. And we configured R1 to redistribute BGP
> into OSPF
> (but it could be EIGRP, no difference).
> R1 doesn't have any BGP peer, but just a network
> statement for
> 1.0.0.0/8 and a static to null0.
>
> ---
>
> R1 config :
> router ospf 1
> redistribute bgp 1
> network 192.168.1.0 0.0.0.255 area 0
> !
> router bgp 1
> no synchronization
> bgp redistribute-internal
> network 1.0.0.0
> no auto-summary
> !
> ip route 1.0.0.0 255.0.0.0 Null0
>
> ---
>
> R2 config :
> router ospf 1
> log-adjacency-changes
> network 192.168.1.0 0.0.0.255 area 0
>
> ---
>
> I used to think that redistribution was done by
> "scanning"
> the routing table and by picking the entries
> matching the criteria
> (for instance, the entries learnt via BGP).
> Here, 1/8 appears in the bgp table but isn't
> installed in the routing
> table (appearing as a "connected" static) :
>
> R1#sh ip bgp
> BGP table version is 2, local router ID is
> 192.168.1.1
> Status codes: s suppressed, d damped, h history, *
> valid, > best, i - internal
> Origin codes: i - IGP, e - EGP, ? - incomplete
>
> Network Next Hop Metric
> LocPrf Weight Path
> *> 1.0.0.0 0.0.0.0 0
> 32768 i
>
>
> R1#sh ip ro 1.0.0.0
> Routing entry for 1.0.0.0/8
> Known via "static", distance 1, metric 0
> (connected)
> Redistributing via ospf 1
> Advertised by ospf 1
> Routing Descriptor Blocks:
> * directly connected, via Null0
> Route metric is 0, traffic share count is 1
>
> But the route 1/8 is redistributed into OSPF :
>
> R2#sh ip ro 1.0.0.0
> Routing entry for 1.0.0.0/8
> Known via "ospf 1", distance 110, metric 1, type
> extern 2, forward metric 64
> Last update from 192.168.1.1 on Serial1/0,
> 00:13:38 ago
> Routing Descriptor Blocks:
> * 192.168.1.1, from 192.168.1.1, 00:13:38 ago, via
> Serial1/0
> Route metric is 1, traffic share count is 1
>
> When I replace the static to null0 by a static to a
> next-hop addy, the route is no longer
> redistributed.
>
> I would like to understand what is the logic behind
> that.
> When we redistribute from BGP to an IGP protocol, is
> it the routes from the routing
> table or from the BGP table that must be taken into
> consideration ?
>
> Cheers,
>
> Nicolas.
>
>
This archive was generated by hypermail 2.1.4 : Mon Feb 02 2004 - 09:07:36 GMT-3