[NTLUG:Discuss] Redhat 7.2, iptables & qpopper

[Michael Patrick]

On Mon, Feb 04, 2002 at 12:11:07PM -0500, Stan Tigrett wrote:

<snip problem statement and nice supporting info>

> Here are my current iptables rules:
> #begin firewall
> modprobe iptable_nat
> /sbin/iptables -F
> /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
> /sbin/iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 -j DNAT --to 192.168.1.100:80
> /sbin/iptables -t nat -A POSTROUTING -p tcp -d 192.168.1.1 -s 192.168.1.0/24 --dport 80 -j SNAT --to 192.168.1.100
> /sbin/iptables -A INPUT -s 0/0 -p tcp --destination-port 110 -j ACCEPT
> echo 1 > /proc/sys/net/ipv4/ip_forward
> #end firewall
> 
> And iptables -L yields:
> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination
> ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:pop3
> 
> Chain FORWARD (policy ACCEPT)
> target     prot opt source               destination
> 
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination
> 

Stan,

I notice you don't have a rule for SSH or SMTP.  Why do you have an explicit rule for POP3?  I tried your rule on one my systems and it didn't seem to bother anything.  Are you certain pop3 is bound to EXINT?  I know telnetting to it from the inside works, so that could be a non-issue.

Is it possible that your upstream provider is blocking pop3?  Do you see you connection packets arrive if you run a tcpdump on the firewall while connecting?

Michael