From: secondie (secondie@gmail.com)
Date: Wed Aug 09 2006 - 22:11:23 ART
I agree with Chris. I initially did the calculation and then put it away
as it looked way off and allowed more routes to leak than I would ever
want to. But on the other hand assuming this is a test scenario, this is
what I think the answer (with explanation) may be:
Just the third octet calculations
binary for route .4.0 = 0000 0100
binary for route .5.0 = 0000 0101
binary for route .21.0 = 0001 0101
As only first three bits must match, my answer would 16+3 = 19 bits
or 200.1.0.0/19.
-secondie
csica wrote:
> Hi Patri,
>
> If I understand what you're trying to do, you're looking for a prefix-list
> that will match the same routes as your access-list 1 below. The problem
> with this is in how prefix-lists and access-lists use the mask field. An
> access-list is more of a binary calculation. The mask is used to determine
> which bits to match. Prefix-lists do not function in this way. They were
> designed to filter ip routes based on the network and the actual subnet
> mask. You could use a summary prefix-list, however, based on your
> requirement below, it would match too many routes. Im not sure if this is
> what you are trying to accomplish, but I hope this helps.
>
> Regards,
> Chris
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Patricia Loreal
> Sent: Wednesday, August 09, 2006 6:46 PM
> To: Bizzell, Keith
> Cc: Aaron Pilcher; Cisco certification
> Subject: Re: ACL 2 Prefix-list
>
> LOL Guys, you are going to kill me =)
>
> I need a prefix-list to make a match for only this routes:
>
> 200.1.4.0/24
> 200.1.5.0/24
> 200.1.21.0/24
>
> or maybe a prefix-list to make a match for this other ones:
>
> 200.1.1.0
> 200.1.22.0
>
> The receiving routes are this one:
> 200.1.1.0
> 200.1.4.0
> 200.1.5.0
> 200.1.21.0
> 200.1.22.0
>
> Ohhhh and 1 line of the prefix-list statement is allowed to do, no 2 line
> statements no 3 lines, just 1 Statement
> Opinions are appreciated
> Patri.
>
>
>
>
> On 8/9/06, Bizzell, Keith <keith.bizzell@eds.com> wrote:
>> Patri - Assuming you have each subnet assigned to an interface, it would
>> look like this:
>>
>> Access-list 1 permit 200.1.1.0 0.0.23.0
>>
>> R2(config)#do show ip route list 1
>> C 200.1.4.0/24
>> C 200.1.21.0/24
>> C 200.1.5.0/24
>> C 200.1.22.0/24
>> C 200.1.1.0/24
>>
>> Of course, that matches more than just those subnets. Those just happen
>> the be the only ones configured on the router. Same thing applies to
>> your access list with the 0.0.17.0 wildcard. See what happenes when I
>> configure 200.1.23.0/24 on a loopback, using the same access-list:
>>
>> R2(config-if)#do show ip route list 1
>> C 200.1.4.0/24
>> C 200.1.21.0/24
>> C 200.1.5.0/24
>> C 200.1.23.0/24
>> C 200.1.22.0/24
>> C 200.1.1.0/24
>>
>> HTH!
>>
>> Keith
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> Patricia Loreal
>> Sent: Wednesday, August 09, 2006 12:57 PM
>> To: Aaron Pilcher
>> Cc: Cisco certification
>> Subject: Re: ACL 2 Prefix-list
>>
>> Hi Aron,
>>
>> Thanks for your feedback, you are very gentle.
>>
>> But I'm looking for a prefix-list that matches this routes only
>> R1(config)#access-list 1 permit 200.1.4.0 0.0.17.0
>>
>> R1#show ip route list 1
>> C 200.1.4.0/24
>> C 200.1.5.0/24
>> C 200.1.21.0/24
>>
>> like the access-list does, but for this routes only:
>>
>> 200.1.1.0
>> 200.1.4.0
>> 200.1.5.0
>> 200.1.21.0
>> 200.1.22.0
>>
>> Thanks
>> Patri.
>>
>>
>> On 8/9/06, Aaron Pilcher <apilcher@itgcs.com> wrote:
>>> Wouldn't a 200.1.0.0 0.0.23.0 be more of an appropriate ACL?
>>>
>>> That said....
>>>
>>> 200.1.0.0/19 ge 32
>>>
>>> -----Original Message-----
>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>>> Of Patricia Loreal
>>> Sent: Wednesday, August 09, 2006 9:10 AM
>>> To: Cisco certification
>>> Subject: ACL 2 Prefix-list
>>>
>>> Hello Dear Group,
>>>
>>> Using this access-list access-list (1) permit 200.1.4.0 0.0.17.0 for
>>> matching this routes:
>>>
>>> 200.1.1.0
>>> 200.1.4.0
>>> 200.1.5.0
>>> 200.1.21.0
>>> 200.1.22.0
>>>
>>> How can I convert the output generated by ACL (1) into 1 Prefix-list
>>> statment
>>>
>>> Thank you very much .!.!.
>>> Kindest Regard
>>> Patri.
>>>
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