NATD & IPFW

[Ryan Merrick]

Brian McCann wrote:

>Hi all.  I'm having an issue with security while trying to get natd to
>work with ipfw.  I got my ipfw rules working great, so I added the natd
>line in:
>
>  ipfw add divert 8668 all from any to any via $EXTERNAL_INTERFACE
>
>But I can't do anything (ping, fetch, etc) until I add:
>  ipfw add pass all from any to any
>
>Now, I may be wrong, but doesn't this pretty much open the box up?  I
>tried changing the first "any" to my internal network, but that didn't
>work, and I know I've got to be missing something.
>
>If anyone would like to help me off-list, I could send you a copy of my
>rule set if you'd like.
>
>Thanks in advance,
>--Brian
>
>
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>  
>
Hello,

The best way to learn about your firewall is to log all denyed packets 
and review the log file while trying different programs that access the 
network.

#ipfw add 6500 deny log any to any

#tail -f /var/log/security

Then create rules based on what shows up in the logs.

-Ryan