Solved: bgp ip prefix-list

lkadlik · ‎07-21-2010

I want to have a prefix list that will permit a /16 address block as well as any networks within the /16. In other words the network could have networks

172.20.10.0/24

172.20.21.0/24

instead of allowing the individual networks I wanted to all the whole /16 in one line in the prefix list

Can i do this using the ge command ?

ip prefix-list XXX permit 172.20.0.0/16 ge ?

I tried to do " ge 16" and got a message saying "% Invalid prefix range for 172.20.0.0/16, make sure: len < ge-value <= le-value"

Jon Marshall · ‎07-21-2010

If you want to include 172.16.0.0/16 and any subnets of that then you should use -

172.16.0.0/16 le 32

which means the first 2 octets must match 172.16. and then you can have combination of subnet mask after that ie. 17, 18, 19 -> 32.

Jon

View solution in original post

Tharak Abraham · ‎07-21-2010

please try:-

ip prefix-list XXX permit 172.20.0.0/16 le 24

This means check the first 16 bits in the mask and it should be less than 24 !

If you want more precise over teh networks to be advertised, you may need to put lesser bits instead of 24, say 19.

Hope to help

lkadlik · ‎07-21-2010

Hi,

Thank you. I will try that and let you know

Jon Marshall · ‎07-21-2010

If you want to include 172.16.0.0/16 and any subnets of that then you should use -

172.16.0.0/16 le 32

which means the first 2 octets must match 172.16. and then you can have combination of subnet mask after that ie. 17, 18, 19 -> 32.

Jon

lkadlik · ‎07-21-2010

So if i want to include the /24 for 172.16.3.0 and any subnets within it I would do

ip prefix-list x permit 172.16.3.0/24 le 24

correct ?

royalblues · ‎07-21-2010

As Jon said in his earlier post, the prefix list should be

ip prefix-list BEACON_MUTUAL_WARWICK permit 172.16.3.0/24 le 32

This will include subnet 172.16.3.0/24 and also subnets within it

172.16.3.0/27,

172.16.3.32/28 etc etc

HTH

Narayan