Linux IP Masquerade HOWTO - The Linux Documentation Project

Linux IP Masquerade HOWTO
Table of Contents
Chapter 7. Frequently Asked Questions
7.10. ( Dial on Demand ) − Can I use Diald or the Dial−on−Demand feature of PPPd with IP
MASQ?...............................................................................................................................................124
7.11. ( Apps ) − What applications are supported with IP Masquerade?............................................124
7.12. ( Distro Setup ) − How can I get IP Masquerade running on Redhat, Debian, Slackware,
etc.?.....................................................................................................................................................125
7.13. ( Timeouts ) − Connections seem to break if I don't use them often. Why is that?....................125
7.14. ( Odd Behavior ) − When my Internet connection first comes up, nothing works. If I try
again, everything then works fine. Why is this?.................................................................................125
7.15. ( MTU ) − IP MASQ seems to be working fine but some sites don't work. This usually
happens with WWW and some FTP sites..........................................................................................126
7.15.1. Enabling PMTU Clamping for PPPoE and some PPP Users:...........................................127
7.15.2. Clamping the MSS via IPTABLES:..................................................................................127
7.15.3. Changing the External MTU of the MASQ server:..........................................................128
7.15.4. Changing the MTU of various operating systems:............................................................128
7.16. ( FTP ) − MASQed FTP clients don't work................................................................................132
7.17. ( Performance ) − IP Masquerading seems slow........................................................................132
7.18. ( PORTFW ) − IP Masquerading with PORTFWing seems to break when my line is idle
for long periods...................................................................................................................................134
7.19. ( PORTFW − Locally ) − I can't reach my PORTFWed server from the INTERNAL lan........134
7.20. ( Logs ) − Now that I have IP Masquerading up, I'm getting all sorts of weird notices and
errors in the SYSLOG log files. How do I read the IPTABLES/IPCHAINS/IPFWADM firewall
errors?.................................................................................................................................................135
7.21. ( Log Reduction ) − My logs are filling up with packet hits due to the new "stronger"
rulesets. How can I fix this?................................................................................................................140
7.22. ( MASQ Security ) − Can I configure IP MASQ to allow Internet users to directly contact
internal MASQed servers?..................................................................................................................140
7.23. ( Free Ports ) − I'm getting "kernel: ip_masq_new(proto=UDP): no free ports." in my
SYSLOG files. Whats up?..................................................................................................................140
7.24. ( SETSOCKOPT ) − I'm getting "ipfwadm: setsockopt failed: Protocol not available"
when I try to use IPPORTFW!............................................................................................................141
7.25. ( SAMBA ) − Microsoft File and Print Sharing and Microsoft Domain clients don't work
through IP Masq!................................................................................................................................141
7.26. ( IDENT ) − IRC won't work properly for MASQed IRC users. Why?.....................................142
7.27. ( IRC DCC ) − mIRC doesn't work with DCC Sends.................................................................142
7.28. ( IP Aliasing ) − Can IP Masquerade work with only ONE Ethernet network card?.................142
7.29. ( Multiple−LANs ) − I have two MASQed LANs but they cannot communicate with each
other!...................................................................................................................................................143
7.30. ( SHAPING ) − I want to be able to limit the speed of specific types of traffic.........................143
7.31. ( ACCOUNTING ) − I need to do accounting on who is using the network.............................143
7.32. ( MULTIPLE IPs − DMZ segments) − I have several EXTERNAL IP addresses that I
want to PORTFW to several internal machines. How do I do this?...................................................144
7.33. ( 1:1 NAT ) − I'd like to do 1:1 NAT but I can't figure out how to do it....................................145
7.34. ( Netstat ) − I'm trying to use the NETSTAT command to show my Masqueraded
connections but its not working..........................................................................................................146
7.35. ( VPNs ) − I would like to get Microsoft PPTP (GRE tunnels) and/or IPSEC (Linux
SWAN) tunnels running through IP MASQ.......................................................................................146
7.36. ( Games ) − I want to get the XYZ network game to work through IP MASQ but it won't
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