Red Hat Bugzilla – Bug 48284
Port forwarding (+masq?) can freeze kernel
Last modified: 2007-04-18 12:34:36 EDT
Description of Problem:
Set up Masq + port forwarding in rc.local:
/sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A PREROUTING -t nat -p tcp -d $EXT --dport $DPORT -j DNAT --to $INT:$DPORT
iptables -A OUTPUT -t nat -p tcp -d $EXT --dport $DPORT -j DNAT --to $INT:$DPORT
echo 1 > /proc/sys/net/ipv4/ip_forward
use the port forwarding for a while, watch it work fine (LimeWire on a win2k box)
kernel will hang, no oops, nothing in logs, nothing on screen. no response to pings
when running gnutella on a box behind the machine, It stays up maybe 5-20minutes.
when not running gnutella (but lots of other network traffic) it stays up indefinitely
Steps to Reproduce:
Standard RH7.1 installation, all updates installed. Kernel "2.4.3-12 #1 Fri Jun 8 15:05:56 EDT 2001 i686 unknown"
50 ip aliases were present on eth1 (200-250), the box forwarded to, was on the subnet with eth1:201 as gateway
seems to be related to having 2 realtek network cards installed, switching to hp100 cards seems to have resolved problem.
The realteks also caused problems (same total hang as above) when routing between two alias interfaces (eth1:100 and eth1:200).
Can you retry with current errata kernels? :-)
sorry, I don't have that old box anymore...
but I'm doing similar stuff now on a newer kernel with no problems.