BGP basic question

[The_guroo_2]

Guys can someone plz tell me th eprefix-list config what is le32 means

ip-prefix list 10 permit 192.168.1.0/24 le 32

so if i write

ip-prefix list 10 permit 192.168.1.0/24

what is the difference

what abt ge concept

Thanks guys

[Reza Sharifi]

Hi,

The difference is that

ip-prefix list 10 permit 192.168.1.0/24 is an exact match only for /24

but

ip-prefix list 10 permit 192.168.1.0/24 le 32 matches /24 and all the prefixes up to 32

HTH

Reza

[Talha Ansari]

Hi Reza,

Thanks for your clarification... you are right on the prefix list match up of those specified for /24 and those specified le 32.

Hi Guroo,

Typically le and ge are used in complex scenarios like for example say suppose your router is learning routes of one network but different subnets :

172.168.0.0 /18

172.168.192.0 /24

172.168.193.0 /28

172.168.209.0 /26

.

.

.

and so on

And from the above routes you intend to permit routes whose subnet mask ranges from /18 to /26... so a prefix list can be created as below :

ip prefix-list 10 permit 172.168.0.0/16 ge 18 le 26

And this could be called in some route-map or distribute-list and applied as a filter or used for some manupulation. This would even permit the routes which have subnet mask of /19 /20 and so on till /26.

Hope that helps....

Regards,

Talha

Message was edited by: Talha Ansari