[c-nsp] BGP Flap Problem

[Stephen Wilcox]

your externally learned routes are flapping?

they probably have a next hop thats learned via bgp which overrides the igp, and then ends up being circular (next hop bgp to a next hop bgp back to itself, rinse, repeat)

check the next hop of the ebgp session, consider next-hop-self.

[thats a possibility, it might be wrong, hard to tell from the info below]

Steve

On Thu, Dec 07, 2006 at 12:58:13PM -0500, Alexandra Alvarado wrote:
> Hello,
> 
>  
> 
>  
> 
> I have configured MP-BGP but some networks go and come every 30 second. What
> could be the reason to this behavior? The configuration is like this:
> 
>  
> 
> Router1 (10.101.11.233)
> 
>  
> 
> router bgp 65000
> 
>  bgp log-neighbor-changes
> 
>  neighbor 10.101.11.255 remote-as 65000
> 
>  neighbor 10.101.11.255 description gye_pe7200_t
> 
>  neighbor 10.101.11.255 update-source Loopback0
> 
> !
> 
>  address-family ipv4
> 
>  no neighbor 10.101.11.255 activate
> 
>  no auto-summary
> 
>  no synchronization
> 
>  exit-address-family
> 
>  !
> 
>  address-family vpnv4
> 
>  neighbor 10.101.11.255 activate
> 
>  neighbor 10.101.11.255 route-reflector-client
> 
>  neighbor 10.101.11.255 send-community extended
> 
> exit-address-family
> 
> !         
> 
> ip classless
> 
> no ip http server
> 
>  
> 
> Router2 (10.101.11.255)
> 
>  
> 
> router bgp 65000
> 
>  bgp router-id 10.101.11.255
> 
>  bgp log-neighbor-changes
> 
>  neighbor 10.101.11.233 remote-as 65000
> 
>  neighbor 10.101.11.233 description rrgyempls
> 
>  neighbor 10.101.11.233 update-source Loopback0
> 
> !
> 
>  address-family ipv4
> 
>  no neighbor 10.101.11.233 activate
> 
>  no auto-summary
> 
>  no synchronization
> 
>  exit-address-family
> 
>  !
> 
>  address-family vpnv4
> 
>  neighbor 10.101.11.233 activate
> 
>  neighbor 10.101.11.233 send-community extended
> 
>  exit-address-family
> 
>  !
> 
>  
> 
>  
> 
> lab_rrgyempls#show ip bgp vpnv4 all nei 10.101.11.255 rout
> 
> BGP table version is 271, local router ID is 10.101.11.233
> 
> 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
> 
> Route Distinguisher: 19169:1
> 
> *>i10.10.51.0/27    10.101.11.255            0    100      0 ?
> 
> *>i10.101.12.248/32 10.101.11.255            0    100      0 19169 ?
> 
> *>i10.101.12.255/32 10.101.11.255            0    100      0 ?
> 
> *>i10.201.12.64/26  10.101.11.255            0    100      0 ?
> 
> *>i10.201.12.128/26 10.101.11.255            0    100      0 19169 ?
> 
> *>i200.93.195.0     10.101.11.255            0    100      0 19169 i
> 
> Route Distinguisher: 65000:1
> 
> *>i201.218.37.0     10.101.11.255            0    100      0 ?
> 
>  
> 
> Total number of prefixes 7 
> 
>  
> 
> lab_rrgyempls#show ip bgp vpnv4 all nei 10.101.11.255 rout
> 
> BGP table version is 274, local router ID is 10.101.11.233
> 
> 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
> 
> Route Distinguisher: 19169:1
> 
> *>i10.10.51.0/27    10.101.11.255            0    100      0 ?
> 
> *>i10.101.12.255/32 10.101.11.255            0    100      0 ?
> 
> *>i10.201.12.64/26  10.101.11.255            0    100      0 ?
> 
> Route Distinguisher: 65000:1
> 
> *>i201.218.37.0     10.101.11.255            0    100      0 ?
> 
>  
> 
> Total number of prefixes 4 
> 
>  
> 
> lab_rrgyempls#
> 
>  
> 
> Thanks
> 
>  
> 
>  
> 
> A.A.A.A.
> 
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-- 
Stephen J. Wilcox
BSc (Hons).  CCIE #10730
Technical Director, Telecomplete
http://www.telecomplete.co.uk/