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Old 02-19-2005, 10:28 AM   #1
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Dual-homed Box won't forward packets

Ok, so I was using Redhat 7 (ipchains) and now I have upgraded to Fedora Core 3 (iptables), so at least I know I am using the latest techonologies.

I have bought Robert Ziegler's book "Linux Firewalls" which is all very interesting but my problem is absolutely no traffic at all is passing out.

I have a standard configuration with eth0 facing Internet and eth1 on the LAN side. All my iptables policies are set to ACCEPT. I have a '1' in /proc/sys/net/ipv4/ip_forward which mattered with RH7, dunno if still does.

I've checked my route table which looks fine, its quite obvious that packets destined for the Internet should be routed out on interface eth0.

So why the **** doesn't it forward packets?

I need to know if there are any gotchas out there which I don't know about.

Is there anything I've missed?

Thanks in advance,
Old 02-19-2005, 10:33 AM   #2
Registered: Mar 2003
Location: Scotland
Distribution: Slackware, RedHat, Debian
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Are you trying to masquerade connections? Take a look at this:
Old 02-19-2005, 02:04 PM   #3
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Thanks for the lead. The article shows that Fedora IP_Forwarding flag has moved cf RH 7. However, this alone did not solve. Found
which says you need to
echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
echo 1 > /proc/sys/net/ipv4/conf/eth1/proxy_arp
to enable address resolution protocol but thanks anyway.

Best Google search on words:
netfilter route "net.ipv4.ip_forward" genmask
because the routing table needs to be checked as well as the firewall



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