Ipchains Woes

[David A. Sinck]

\_ SMTP quoth Steve Holmes on 2/26/2002 04:52 as having spake thusly:
\_
\_ I know, but as soon as I make default policy to DENY on the input chain,
\_ all connectivity to the outside is lost.  Here was a basic set of rules at
\_ my last test.
\_ ipchains -P input DENY
\_ ipchains -A input -i lo -j ACCEPT
\_ ipchains -A input -i eth0 -j ACCEPT
\_ ipchains -P forward DENY
\_ ipchains -A forward -s 192.168.x.y/24 -j MASQ
\_ ipchains -P output -j ACCEPT
\_ Now at this point I tried adding something like
\_ ipchains -A input -i eth1 -p ! -y --dport 1025:65535 -j ACCEPT

ipchains have been a while, but doesn't -p require an argument like
'tcp' or 'udp'?  That feels like a tcp rule.

\_ to the chains with no change; At this point, I can get around fine on the
\_ local area network but from any machine inside or the firewalled machine
\_ itself, I cannot ping anything other than the DNS itself.  

Some distros auto punch DNS entries into the firewall as part of the
network setup.  

Keep in mind that *most* dns traffic and pings aren't tcp.


\_ That is interesting in itself.  My Static ip is 24.221.xx.xx

<aside>
Does it make anyone else nervous this thread:

--> my firewall doesn't work
--> I seem to currently only get it to work when it's wide open
--> my internal IPs are
--> my external IP is

To me, it *seems* like an invitation for malcontents to portscan you
box so far that you'll have to get clearance from Customs to bring it
back in.  

It's nice that you're trusting and all, but there are some
ne'er-do-wells out there and google crawls the list archives
occassionally.
</aside>

\_ and the dns is
\_ 24.221.x.y and I cn ping that with no trouble but I cannot ping other IP
\_ address in other network address ranges.  Not sure why that be the case.
\_ All other protocols are "no go".

Well, can you surf?  :-)

\_ Just messing around, but as soon as I added a rule like
\_ ipchains -A input -i eth1 -j ACCEPT
\_ then it was wide open.  that makes sense to me and is what I would expect.
\_ So at least ipchains is recognizing the network devices.  I do find it
\_ interesting that ipchains -L did not specifically mention the device
\_ names.  It showed ----lo but the entries that should have been eth0 and
\_ eth1 showed up as ------.  Shouldn't it have shown the eth devices
\_ clearly?
\_ 
\_ Thanks for the help so far.

I've always run -nvL ... check the docs for meanings.

David