From: Scott M Vermillion (scott_ccie_list@it-ag.com)
Date: Fri Mar 27 2009 - 17:16:13 ART
Bit of a belated response here but I've been pounding away on SP and
getting further and further behind on my list traffic. Congrats to
all you new CCIEs out there, BTW.
You need some solid prefix-list theory under your belt (there are some
great blog posts out there on the topic) but then you just need time
on the CLI to see how things behave for yourself. You should realize
right off the bat that if you specify a "/8" in the prefix part of
your prefix-list, none of the bits in positions 9 thru 32 matter, so
they should be all zeros in your command. The less obvious part is
what happens to that 'le 32' you threw on the end there. It's
basically inferred/encompassed by the 'ge' operator and so is
redundant. IOS will politely and discretely ignore your prefix-list
faux pas.
Rack1R1(config)#ip prefix blah seq 5 permit 1.1.1.1/8 ge 24 le 32
Rack1R1(config)#do sh ip prefix
ip prefix-list blah: 1 entries
seq 5 permit 1.0.0.0/8 ge 24
Rack1R1(config)#ip prefix blah seq 10 permit 2.0.0.0/8 ge 24 le 31
Rack1R1(config)#do sh ip prefix
ip prefix-list blah: 2 entries
seq 5 permit 1.0.0.0/8 ge 24
seq 10 permit 2.0.0.0/8 ge 24 le 31
On Mar 22, 2009, at 6:53 , Ruhann wrote:
> the seq number is just a numerical place holder for the entries of
> prefix
> list "NET".
> you wont be able to apply both lines on the same router as the first
> one
> would get a default seq-number of 5 and the second line will shout
> at you,
> something like "seq already exists"
>
> then, x.x.x.x/x does not really equite to much in cisco land, so I
> cant
> assist with the prefix difference between the two, but as for the
> length of
> the subnet mask, yes there is difference.
> the first command would allow subnet lengths from /24 up to /32 (host
> routes) and the second only up to a length of 26 bits, depending on
> what the
> magic /x value is.
>
> hth :)
>
>
>
> On Sat, Mar 21, 2009 at 9:30 PM, Raghav Bhargava <raghavbhargava12@gmail.com
>> wrote:
>
>> hi Experts,
>> What is the difference between these 2 commands:-
>>
>> ip prefix-list NET permit 1.1.1.1/8 ge 24 le 32
>>
>> AND
>>
>> ip prefix-list NET seq 5 permit x.x.x.x/x ge 24 le 26
>>
>> What is the significance of not using the sequence number in the
>> first
>> Command. Also is the first command correct. I doubt it???
>>
>> Please advise.
>>
>> --
>> Warm Regards
>> Raghav
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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>>
>>
>>
>>
>>
>>
>>
>
>
> --
> <ruhann>
>
>
> Blogs and organic groups at http://www.ccie.net
>
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