[149362] in North American Network Operators' Group
Re: Question about prefix list
daemon@ATHENA.MIT.EDU (Randy)
Wed Feb 1 23:14:35 2012
Date: Wed, 1 Feb 2012 20:13:38 -0800 (PST)
From: Randy <randy_94108@yahoo.com>
To: nanog@nanog.org, Ann Kwok <annkwok80@gmail.com>
In-Reply-To: <CACwqZxjZwUDqbcB+PUM=0+noH9oWogtEeXPxAz_vLed68fxf8w@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Ann,
the commas not withstanding, the le/ge operands as applicable to prefix-lis=
ts simply mean "less-than or equal-to" or greater-than or "equal-to" wrt ne=
tmasks in CIDR speak.
In you prefix-list below, the le operand means -
allow following ranges:
/22,/23,/24 deny all else
for the /21
it means allow /21 thru /24
Anything without an operand means an exact-match(permit/deny)
Homework for you:
What do the following do:
1) ip prefix-list foo deny 0.0.0.0/0 le32
2) ip prefix-list foo permit 0.0.0/0 le 32
Understand the above and you will understand how operands work in prefix-li=
sts.
./Randy
--- On Wed, 2/1/12, Ann Kwok <annkwok80@gmail.com> wrote:
> From: Ann Kwok <annkwok80@gmail.com>
> Subject: Question about prefix list
> To: nanog@nanog.org
> Date: Wednesday, February 1, 2012, 6:32 AM
> 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=A0 "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
>
