From: Mujeeb Sarwar (mujeebsarwar@gmail.com)
Date: Wed Dec 31 2008 - 06:36:29 ARST
Hi,
This is correct behavior because some attributes preserves within
Confederation like Next Hop,MED & Local Preference. Although sub AS of a
confederation establishes eBGP sessions but some attributes will remain
preserve as in iBGP.
Regards,
Mujeeb
On Wed, Dec 31, 2008 at 12:03 PM, Xiaobo Zhu <xiaobo@zhu.net> wrote:
> Hi,
> Sorry for that long subject, hope I've described the question clearly with
> it. I will explain it in detail anyway.
> Here is the scenario.
> (
>
> 6.6.6.6/24)R6(192.168.16.0/24)R1(192.168.12.0/24)R2(192.168.23.0/24)R3(192.168.35.0/24)R5(5.5.5.5/24
> )
> and R2 has a loopback interface with IP address 2.2.2.2/24
> R6 is in BGP AS 6, R1 and R2 are in BGP AS 12, R3 is in BGP AS 3 and R5 is
> in BGP AS 5.
> When I advertise R5's loopback interface to the network with the command
> network 5.5.5.0 mask 255.255.255.0, R3 can install the entry with no
> difficulty, but R2 failed.
> It seems that R3 does not change the next hop of 5.5.5.0/24 entry to
> 192.168.23.3(I will paste the output below).
> The question is just as the subject of this email, as R1, R2 and R3 are in
> the same are in the same confederation, R3 should take R2 as an EBGP
> neighbor in its point of view. Why R3 does not change the next hop of the
> 5.5.5.0/24 entry when forward it to R2.
> Many thanks and best wishes for the coming new year!
> Cheers, Xiaobo
>
> The following are the running configuration.
> ===============================
> R1#show running-config | begin router bgp
> router bgp 12
> no synchronization
> bgp log-neighbor-changes
> bgp confederation identifier 2
> neighbor 192.168.12.2 remote-as 12
> neighbor 192.168.12.2 next-hop-self
> neighbor 192.168.16.6 remote-as 6
> no auto-summary
> --------------------------------------------------------------
> R2#show running-config | begin router bgp
> router bgp 12
> no synchronization
> bgp log-neighbor-changes
> bgp confederation identifier 2
> bgp confederation peers 3
> network 2.2.2.0 mask 255.255.255.0
> neighbor 192.168.12.1 remote-as 12
> neighbor 192.168.12.1 next-hop-self
> neighbor 192.168.23.3 remote-as 3
> no auto-summary
> --------------------------------------------------------------
> R3#show running-config | begin router bgp
> router bgp 3
> no synchronization
> bgp log-neighbor-changes
> bgp confederation identifier 2
> bgp confederation peers 12
> neighbor 192.168.23.2 remote-as 12
> neighbor 192.168.35.5 remote-as 5
> no auto-summary
> --------------------------------------------------------------
> R5#show running-config | begin router bgp
> router bgp 5
> no synchronization
> bgp log-neighbor-changes
> network 5.5.5.0 mask 255.255.255.0
> neighbor 192.168.35.3 remote-as 2
> no auto-summary
> --------------------------------------------------------------
> R6#show running-config | begin router b
> router bgp 6
> no synchronization
> bgp log-neighbor-changes
> network 6.6.6.0 mask 255.255.255.0
> neighbor 192.168.16.1 remote-as 2
> no auto-summary
> --------------------------------------------------------------
> R2#show ip bgp
> BGP table version is 5, local router ID is 2.2.2.2
> Status codes: s suppressed, d damped, h history, * valid, > best, i -
> internal,
> r RIB-failure, S Stale
> Origin codes: i - IGP, e - EGP, ? - incomplete
>
> Network Next Hop Metric LocPrf Weight Path
> *> 2.2.2.0/24 0.0.0.0 0 32768 i
> * 5.5.5.0/24 192.168.35.5 0 100 0 (3) 5 i
> *>i6.6.6.0/24 192.168.12.1 0 100 0 6 i
>
>
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