Someone on this list wrote recently wondering if they would need to recompile their kernel inorder to get ip masquerading working.
They are using a stock kernel version 2.0.38 that came with slink and said that when they executed the command... /sbin/ipfwadm -F -p deny they got the following... ipfwadm: setsockopt failed: Protocol not available. I suggested first using... echo "1" > /proc/sys/net/ipv4/ip_forward but this did not seem to help. Does the stock kernel not support ip masquerading or does the problem lie elsewhere. TIA