Re: Change outbound ICMP source

[Nathaniel Hall <nathaniel.d.hall@gmail.com>]

R. DuFresne wrote:

> On Mon, 10 Apr 2006, Nathaniel Hall wrote:
>
>> I have been trying to figure out how to change the source IP address
of an
>> ICMP packet that originates from the firewall.  Here is my application.
>>
>> Instead of dropping a packet I reject it with ICMP host unreachable
messages.
>> I would like to make it appear that the firewall isn't there, so I
would like to
>> change the source IP address to be that of our upstream router.  How
would
>> I go about doing this?
>
> by blocking the ICMP's at that upstream router.

That doesn't achieve what I want.  If a TCP connection is rejected at
the firewall, then blocking ICMP at the upstream router will block the
host-unreachable from going out, not make it seem as if the router is
the source.

-- 
Nathaniel Hall, GSEC GCFW GCIA