From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Thu Jan 08 2004 - 22:52:57 GMT-3
Yes you can. The class of an address is determined by the first
four most significant bits:
Class A: 0xxxxxxx
Class B: 10xxxxxx
Class C: 110xxxxx
Class D: 1110xxxx
Class E: 1111xxxx
So if you want to match on just the class, you can do it with a
standard access-list.
Access-list 1 permit 0.0.0.0 127.255.255.255 <-- Class A
Access-list 1 permit 128.0.0.0 63.255.255.255 <-- Class B
Access-list 1 permit 192.0.0.0 31.255.255.255 <-- Class C
If you want to match classful networks with classful masks (i.e.
class A with /8, class B with /16, and class C with /24), you need an
extended access-list or an ip prefix-list.
Simply take the above syntax and add the mask as the destination:
Class A:
Access-list 100 permit ip 0.0.0.0 127.255.255.255 host 255.0.0.0
Class B:
Access-list 100 permit ip 128.0.0.0 63.255.255.255 host 255.255.0.0
Class C:
Access-list 100 permit ip 192.0.0.0 31.255.255.255 host 255.255.255.0
Note that this extended ACL syntax can only be applied in BGP.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 708-362-1418 (Outside the US and Canada)
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Kaiser Anwar
> Sent: Thursday, January 08, 2004 7:38 PM
> To: ccielab@groupstudy.com
> Subject: classfull routes with an access list
>
> Hi,
> I was wondering that would it be possible to permit or block classfull
> routes
> with access-list.I know it is done with prefix list.
>
> Thanks
>
>
> Sincerely,
> Kaiser Anwar
> (847) 409-7261
> CCNA, CCNP
> CCSA, MCSE
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Mon Feb 02 2004 - 09:07:38 GMT-3