masquerading question

I have set up a LINUX box as a firewall with IP-masquerading. I think I got it all set up correctly after a multitude of trials, but I still have a question. I have a PPP connection to the ISP and an ethernet internal network.

The masquerading HOWTO lists specific commands for setting up the masquerading:

ipfwadm -F -p deny
ipfwadm -F -a m -S XXX.XXX.XXX.0/24 -D 0.0.0.0/0

with an optional -V YYY.YYY.YYY.YYY or -W ifname as options.

When I test it without the options, everything works fine and I can access the internet and newsgroups from any PC on the internal net.

When I specify the -V option with the internal IP address of the LINUX box, I cannot get out. The same applies, when I use the -W option with eth0 as the ifname. If I specify -W ppp0, then everything is fine again.

Is there a security hole, or is this OK?

Again, the ppp0 is the external connection of the firewall, the eth0 is the internal connection.

Michael Bode
mb@soft-imaging.com
mbodeAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

unicorntechCommented:
This looks to be ok by me - I don't feel there is a security hole here. I would also set up tcpd and the /etc/hosts.allow and the /etc/hosts.deny files ( do a man on tcpd) to deny access to services as well,

Regards,

Jason
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Linux Networking

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.