Linux IP Masquerade HOWTO
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7.13. ( Timeouts ) - Connections seem to break if I don't use them often. Why is that?

IP Masq, by default, sets its timers for TCP session, TCP FIN, and UDP traffic to 15 minutes. It is recommend to use the following settings (as already shown in this HOWTO's /etc/rc.d/rc.firewall-* ruleset) for most users:

Linux 2.4.x with IPTABLES

IPMASQ timeouts are NOT adjustable under IPTABLES

Linux 2.2.x with IPCHAINS:

# MASQ timeouts
#
#   2 hrs timeout for TCP session timeouts
#  10 sec timeout for traffic after the TCP/IP "FIN" packet is received
#  60 sec timeout for UDP traffic (MASQ'ed ICQ users must enable a 30sec 
#     firewall timeout in ICQ itself)
#
/ipchains -M -S 7200 10 60

Linux 2.0.x with IPFWADM:

# MASQ timeouts 
#
#   2 hrs timeout for TCP session timeouts
#  10 sec timeout for traffic after the TCP/IP "FIN" packet is received
#  60 sec timeout for UDP traffic (MASQ'ed ICQ users must enable a 30sec 
#     firewall timeout in ICQ itself) 
#
/sbin/ipfwadm -M -s 7200 10 60

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( Distro Setup ) - How can I get IP Masquerade running on Redhat, Debian, Slackware, etc.?Up( Odd Behavior ) - When my Internet connection first comes up, nothing works. If I try again, everything then works fine. Why is this?