[149351] in North American Network Operators' Group
Re: Question about prefix list
daemon@ATHENA.MIT.EDU (Wouter van der Vaart)
Wed Feb 1 20:44:39 2012
From: Wouter van der Vaart <wouter@terrean.net>
In-Reply-To: <CACwqZxjZwUDqbcB+PUM=0+noH9oWogtEeXPxAz_vLed68fxf8w@mail.gmail.com>
Date: Thu, 2 Feb 2012 02:43:37 +0100
To: Ann Kwok <annkwok80@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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
>=20
> I read this prefix list.
>=20
> Can I know why there is "le 24" after network block in /22 and /21
>=20
> Why don't have "le 24" after /24?
>=20
> I also saw another prefix list before. They use "le 32" instead of =
"le 24"
>=20
> What are their different?
>=20
> 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
>=20
> Thank you so much
