prefix-list problem

[att-sgcops]

I was asked to configure BGP under certain requirements:

AS100 (R6)will not accept any route from As 54 with network mask longer than 20. Since R6 is in AS 100, I configured R6 as following:

router bgp 100

bgp log-neighbor-changes

neighbor 54.1.6.254 remote-as 54

neighbor 54.1.6.254 route-map filter in

ip prefix-list longer20 seq 5 deny 0.0.0.0/0 ge 21

route-map filter permit 10

match ip address prefix-list longer20

But it filter all the network, And the correct answer is different @ prefix-list:

ip prefix-list longer20 seq 5 permit 0.0.0.0/0 le 20.

Can someone explaine to me?

thanks

[mheusinger · Accepted solution]

Hello,

a prefix-list is an access-list ... there is an invisible deny! So better would be:

ip prefix-list longer20 seq 5 deny 0.0.0.0/0 ge 21

ip prefix-list longer20 seq 10 permit 0.0.0.0/0 le 32

or

ip prefix-list longer20 seq 5 permit 0.0.0.0/0 le 20

Hope this helps! Please rate all posts.

Regards, Martin