Thanks you guys for all the answers. I know this is a competitor's content (I'm sorry if I'm breaking ML's rules), but after reading this: http://www.routerie.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=50;t=001706 (the second post)
I finally understood prefix-list's logic. So here's the solution: I'm receiving three prefixes: 10.252.52.0/24, 10.252.60.0/25 and 10.252.114.0/24, and I'd like to filter (i.e. I dont to announce these networks to my neighbor) only the first two using a single prefix-list statement. The catch about prefix-lists is that when they're used WITH an le or ge statement, the number after the network (/whatever), becomes the number of bits matched AND the numbers between le and/or ge statements become the length of subnet mask to be matched So using this logic the best answer would be: ip prefix-list ACL-DENY-SOME seq 5 deny 10.252.48.0/20 ge 24 le 24 ip prefix-list ACL-DENY-SOME seq 10 permit 0.0.0.0/0 le 32 So I'm, not announcing 10.252.[48-63].0 networks (which includes 10.252.52.0, 10.252.60.0 among others), as long as they are received with an EXACT /24 netmask.
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