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RE: BGP Backdoor Routing issue posted 06/29/2007
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The route should be in RIP as well.  The purpose of bgp backdoor is due
to the fact that a route learned via eBGP has an admin of 20.  This is
far superior to that of any IGP.  

So to reach R5 from R4 it is silly to traverse the BGP cloud, when a
perfectly good way to reach R5 is via RIP.  But the route needs to be in
the IGP for any sort of traffic to actually take the backdoor path.

Jason

> -----Original Message-----
> From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
Of
> Mike Kraus (mikraus)
> Sent: Thursday, June 28, 2007 6:11 PM
> To: Sadiq Yakasai; Cisco certification
> Subject: RE: BGP Backdoor Routing issue
> 
> What if you add the mask to your network statement?  (network
150.1.4.0
> mask 255.255.255.0 backdoor)
> 
> -----Original Message-----
> From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
Of
> Sadiq Yakasai
> Sent: Thursday, June 28, 2007 4:37 PM
> To: Cisco certification
> Subject: BGP Backdoor Routing issue
> 
> hi Guys,
> 
> Can someone help out here please? See setup below:
> 
>   (150.1.4.4)
>      lo0
>       |                   rip (155.1.45.0)
>      R4 ------------------------------------------------- R5
>       |                                                       |
>       |                                                       |
>       |ebgp                                                |ebgp
>       |                                                       |
>       |---------------------R3 -----------------------------|
> 
> 
> R4 is advertising lo0 (150.1.4.0) into bgp to R5 (via R3, who is an
ebgp
> peer to R4 as well)
> R4 is doing rip on the link to R5
> 
> R5 is receiving the same route from both protocols (bgp & rip). I have
> confirmed this as you will see later on.
> 
> I issue the network 150.1.4.0 backdoor command on R5, but it doesnt
> install the 150.1.4.0 route in the IP routing table as an rip route
> (which is the reason for the backdoor routing in the first place place
i
> presume).
> 
> Pls is there anything i am not getting right here? I have read all the
> text on it that I can find (Routing TCP/IP vol 2, Internet Routing
> Architecture, BGP Command and Config Handbook, CCO) but to no avail.
> 
> Now i am getting frustrated! I need help! :-)
> 
> 
> R5:
> R5#sh run | b router bgp
> router bgp 5
>  no synchronization
>  bgp log-neighbor-changes
>  network 150.1.4.0 backdoor
>  neighbor 155.1.0.1 remote-as 1
>  no auto-summary
> !
> router rip
>  version 2
>  network 155.1.0.0
>  no auto-summary
> R5#
> R5#sh ip rout | inc 150.1.4
> B       150.1.4.0 [20/0] via 155.1.0.1, 00:30:05    <---------at this
> point, the bgp route is on the ip routing table
> 
> R5#conf t
> R5(config)#router bgp 5
> R5(config-router)#no neighbor 155.1.0.1 remote-as 1
> 
> R5(config-router)# do clear ip rout *
> R5(config-router)#do sh ip rout
> R       150.1.4.0 [120/1] via 155.1.45.4, 00:00:03, Serial0/3/0
> <--------- i clear the bgp neigb and the rip route makes it
> 
>    to the routing table
> 
> R5(config-router)#neighbor 155.1.0.1 remote-as 1   <--------- i
> restore the bgp neig and it reverts!
> R5(config-router)# do clear ip rout *
> *Jun 28 21:28:14.277: %BGP-5-ADJCHANGE: neighbor 155.1.0.1 Up
> R5(config-router)# do clear ip rout * R5(config-router)#do sh ip rout
> B       150.1.4.0 [20/0] via 155.1.0.1, 00:00:03
> 
>
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