Re: the infamous "static" versus "nat"

On 4/5/06, Vahid Pazirandeh <vpaziran_at_yahoo.com> wrote:
> Hi All. Great mail list btw, thanks to everyones input.
>
> Two basic questions.
>
> 1. I've heard the convention of using "static" for low-to-high NATing and
> "nat/global" for high-to-low. Why?

that's the way Cisco designed it. And it's not a "convention": you have to
use these commands precisely that way otherwise the beast won't work.

there are some technical reasons too: static is always a 1-1 mapping.
with nat/global you can have many-to-few mappings, which can fall back
to port-based multiplexing (PAT) if necessary.

but you still have to wonder what the designers were drinking when they
decided that 3 separate commands with vastly different syntax are
called for.

>
> 2. Would someone explain the underlying differences in these two commands? Do
> they achieve the same thing? Assume net1 = 10.1.1.0/24, net2 = 10.2.2.0/24.
>
> A. static (net1, net2) 10.1.1.0 10.1.1.0 netmask 255.255.255.0
> B. static (net2, net1) 10.2.2.0 10.2.2.0 netmask 255.255.255.0
>

you didn't tell us which interface has a higher security level, so I can't
say which of these variants is wrong but I believe one of them is... the
command is "static (high_security_interface, low_security_interface) ..."

> Cheers!

HTH,
  Avishai
>
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--
Avishai Wool, Ph.D.,
Chief Technical Officer,       Algorithmic Security Inc.
                  http://www.algosec.com
*******    Making your firewalls really safe    *******
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