From: Vijay babu (dotcomvijay@gmail.com)
Date: Tue Jul 03 2007 - 06:41:41 ART
Hi Paul,
You are right, I will have to correct my previous post.
Found this link on doing some search.
*Q.* Why does a subnet mask need to be specified when configuring a NAT
address pool?
*A.* The subnet mask is used to double-check the addresses allocated from
the pool. For example, the subnet broadcast address does not get allocated.
The subnet mask must match the size of the subnet into which it is
translated.
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_q_and_a_item0900aecd801ba55a.shtml
Cheers
Vijay
On 7/3/07, paul.cocker@bt.com <paul.cocker@bt.com> wrote:
>
> Hi Vivjay,
>
> Thanks for you response.
>
> I thought there was no field in the IP header for subnet mask, so I'm a
> little confused how it would enter the ISP with a particular subnet
> mask?
>
> Regards,
> Paul
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Vijay babu
> Sent: 03 July 2007 09:51
> To: ccielab@groupstudy.com
> Subject: Re: ip nat pool command
>
> My understanding is...
>
> When the nat pool is defined with
> Ip nat pool XYW 1.1.1.1 1.1.1.50 netmask 255.255.255.0
>
> The nated packet leaving your network is give an ip 1.1.1.1 with a
> subnet
> mask
> of 255.255.255.0. This also means the ISP has provided you a 1.1.1.0
> (entire
> class c)subnet
> for your Internet access.
>
> If nat pool is defined with
> Ip nat pool XYW 1.1.1.1 1.1.1.50 netmask 255.255.255.128
>
> The nated packet is give an ip 1.1.1.1 with network mask 255.255.255.128
> This means your ISP has given you 1.1.1.1 till 1.1.1.126 range of
> ip address for your use.
>
> Cheers
>
> Vijay
>
>
>
>
> On 7/3/07, paul.cocker@bt.com <paul.cocker@bt.com> wrote:
> >
> > Hi All,
> >
> > I'm a little confused what exactly the netmask command does
> >
> > Ip nat pool XYW 1.1.1.1 1.1.1.50 netmask 255.255.255.0
> >
> > How does that differ from
> >
> > Ip nat pool XYW 1.1.1.1 1.1.1.50 netmask 255.255.255.128 ?
> >
> > What's the purpose of it?
> >
> > Regards,
> > Paul
> >
> >
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