BGP route filtering

Unanswered Question
May 9th, 2010

Hi,


Here is the output before applying distribute-list


BGP table version is 3, local router ID is 1.1.1.1
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
*>i192.168.2.0      1.1.2.1                  0    100      0 i
*>i192.168.20.0     1.1.2.1                  0    100      0 i



Here is the following configuration for BGP


ip prefix-list fp seq 10 permit 192.168.2.0/24 ------------  matches exact 192.168.2.0 255.255.255.0  sub-net


router bgp 100
no synchronization
bgp log-neighbor-changes
neighbor 1.1.2.1 remote-as 100
neighbor 1.1.2.1 update-source Loopback1
distribute-list prefix fp in Serial1/1   -----------------------> updates are received from ser 1/1
no auto-summary


the subnet 192.168.2.0/24 is not getting blocked.


I am able to block that subnet by route-map but not with distribute-list command.


Please share the experience


Thanks

Subodh

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Jon Marshall Sun, 05/09/2010 - 18:10

bapatsubodh wrote:


Hi,


ip prefix-list fp seq 10 permit 192.168.2.0/24 ------------  matches exact 192.168.2.0 255.255.255.0  sub-net


router bgp 100
no synchronization
bgp log-neighbor-changes
neighbor 1.1.2.1 remote-as 100
neighbor 1.1.2.1 update-source Loopback1
distribute-list prefix fp in Serial1/1   -----------------------> updates are received from ser 1/1
no auto-summary


the subnet 192.168.2.0/24 is not getting blocked.


I am able to block that subnet by route-map but not with distribute-list command.


Please share the experience


Thanks

Subodh


Subodh


If you want to filter routes coming from a neighbor with a prefix list then you should do it this way -


ip prefix-list fp seq 10 deny 192.168.2.0/24

ip prefix-list fp seq 20 permit 0.0.0.0/0 le 32


router bgp 100

neighbor 1.1.2.1 prefix-list fp in


Jon

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