From: afiddler (afiddler@xxxxxxxxx)
Date: Sun Sep 02 2001 - 13:19:46 GMT-3
Michael, I think I've figured this out. There were a few discrepancies in
Doyle's example. I found that Halabi's backdoor example was clearer (page
326 of the second addition). Doyle's backdoor example is two-way, where he
has a backdoor route defined on both Meribel and Lillehammer. Halabi's
example just has one backdoor route.
What is possibly not made clear in Doyle's example is that only RIP is
running over the serial link between Meribel and Lillehammer. I think the
use of redistribution statements in the configurations of Meribel and
Lillehammer on pages 237 and 238 is misleading, especially when he
redistributes two ways on Meribel and one way on Lillehammer(?). I removed
the redistribution statements altogether, as I think they are unnecessary at
the least. Meribel and Lillehammer are not BGP neighbors, since only RIP is
running on the serial link between them. They are neighbors with Innsbruck
and Cervinia. I also turned off synchronization (Doyle forgets to do this
in several examples). Here is my config from Meribel. Lillehammer's is the
same in concept.
interface Loopback0
ip address 10.50.250.1 255.255.255.255
no ip directed-broadcast
!
interface Loopback1
ip address 10.20.0.1 255.255.0.0
no ip directed-broadcast
!
interface Loopback2
ip address 172.17.0.1 255.255.0.0
no ip directed-broadcast
!
interface Loopback3
ip address 172.29.2.1 255.255.255.0
no ip directed-broadcast
!
interface Loopback4
ip address 192.168.50.1 255.255.255.0
no ip directed-broadcast
!
interface Ethernet0
ip address 192.168.10.1 255.255.255.0
no ip directed-broadcast
!
interface Ethernet1
ip address 10.2.0.1 255.255.0.0
no ip directed-broadcast
!
interface Serial0
ip address 192.168.20.1 255.255.255.0
no ip directed-broadcast
no ip mroute-cache
no fair-queue
clockrate 250000
!
router rip
network 10.0.0.0
network 172.17.0.0
network 172.29.0.0
network 192.168.20.0
network 192.168.50.0
!
router bgp 50
no synchronization
bgp log-neighbor-changes
network 172.17.0.0
network 172.18.0.0 backdoor
neighbor 10.100.83.1 remote-as 100
neighbor 10.100.83.1 ebgp-multihop 2
neighbor 10.100.83.1 update-source Loopback0
neighbor 10.200.60.1 remote-as 200
neighbor 10.200.60.1 ebgp-multihop 2
neighbor 10.200.60.1 update-source Loopback0
no auto-summary
!
ip route 10.100.83.1 255.255.255.255 192.168.10.2
ip route 10.200.60.1 255.255.255.255 192.168.10.4
In my lab I have routers running a few different versions of the IOS,
partially to appreciate the differences in versions, but also in case there
is a bug in one version that is not in the other version(s). Well guess
what, there is a bug relating to the use of backdoor. Here it is from CCO:
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