Question about prefix list

Wouter van der Vaart wouter at terrean.net
Wed Feb 1 19:43:37 CST 2012


Hi Ann,

The le parameter can be included to match all more-specific prefixes within a par ten prefix up to a specified length. FE: 202.168.136.0/22 le 25 will match 202.168.136.0/22 and all prefixes contained therein with a length of 24 or less.

They appear to be blocking everything with a length longer dan /24 (so /25 /26 etc etc.)

the last line doesn't have this because it's only 1 /24 subnet.

Regards,

Wouter
On Feb 1, 2012, at 15:32 , Ann Kwok wrote:

> Hi
> 
> I read this prefix list.
> 
> Can I know why there is "le 24" after network block in /22 and /21
> 
> Why don't have "le 24" after /24?
> 
> I also saw another prefix list before. They use "le 32" instead of  "le 24"
> 
> What are their different?
> 
> ip prefix-list prefix-filter-as100 seq 10 permit 202,168.136.0/22 le 24
> ip prefix-list prefix-filter-as100 seq 20 permit 202,22.92.0/22 le 24
> ip prefix-list prefix-filter-as100 seq 30 permit 202,21.148.0/22 le 24
> ip prefix-list prefix-filter-as100 seq 40 permit 203,178.88.0/21 le 24
> ip prefix-list prefix-filter-as100 seq 50 permit 178.88.74.0/24
> 
> Thank you so much





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