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Old 06-23-2004, 08:35 AM   #1
rendaimedia
LQ Newbie
 
Registered: Apr 2004
Posts: 10

Rep: Reputation: 0
IP Masquerade Problems on RH 9.0


Ok, I know this is a common problem but I have gone through alot of howto's etc and still cant get this running?

I'm trying to share my ppp0 dialup connection from my rh9 box to a XP laptop..

I know how to setup the network and have sucessfully setup samba, ftp, http etc servers on the rh9 box and can access them from the lappy (using direct IP addresses) just the Masquerading wont work...

Here's the script I'm running at boot to setup ipv4 etc:
----------------------------------------------------------------------------------
#!/bin/sh
#
# rc.firewall-2.4
FWVER=0.75
#
# Initial SIMPLE IP Masquerade test for 2.4.x kernels
# using IPTABLES.
#
# Once IP Masquerading has been tested, with this simple
# ruleset, it is highly recommended to use a stronger
# IPTABLES ruleset either given later in this HOWTO or
# from another reputable resource.
#
#
#
# Log:
# 0.75 - Added more kernel modules to the comments section
# 0.74 - the ruleset now uses modprobe vs. insmod
# 0.73 - REJECT is not a legal policy yet; back to DROP
# 0.72 - Changed the default block behavior to REJECT not DROP
# 0.71 - Added clarification that PPPoE users need to use
# "ppp0" instead of "eth0" for their external interface
# 0.70 - Added commented option for IRC nat module
# - Added additional use of environment variables
# - Added additional formatting
# 0.63 - Added support for the IRC IPTABLES module
# 0.62 - Fixed a typo on the MASQ enable line that used eth0
# instead of $EXTIF
# 0.61 - Changed the firewall to use variables for the internal
# and external interfaces.
# 0.60 - 0.50 had a mistake where the ruleset had a rule to DROP
# all forwarded packets but it didn't have a rule to ACCEPT
# any packets to be forwarded either
# - Load the ip_nat_ftp and ip_conntrack_ftp modules by default
# 0.50 - Initial draft
#

echo -e "\n\nLoading simple rc.firewall version $FWVER..\n"


# The location of the iptables and kernel module programs
#
# If your Linux distribution came with a copy of iptables,
# most likely all the programs will be located in /sbin. If
# you manually compiled iptables, the default location will
# be in /usr/local/sbin
#
# ** Please use the "whereis iptables" command to figure out
# ** where your copy is and change the path below to reflect
# ** your setup
#
#IPTABLES=/sbin/iptables
IPTABLES=/usr/local/sbin/iptables
DEPMOD=/sbin/depmod
MODPROBE=/sbin/modprobe


#Setting the EXTERNAL and INTERNAL interfaces for the network
#
# Each IP Masquerade network needs to have at least one
# external and one internal network. The external network
# is where the natting will occur and the internal network
# should preferably be addressed with a RFC1918 private address
# scheme.
#
# For this example, "eth0" is external and "eth1" is internal"
#
#
# NOTE: If this doesnt EXACTLY fit your configuration, you must
# change the EXTIF or INTIF variables above. For example:
#
# If you are a PPPoE or analog modem user:
#
# EXTIF="ppp0"
#
#
EXTIF="ppp0"
INTIF="eth0"
echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF"


#======================================================================
#== No editing beyond this line is required for initial MASQ testing ==


echo -en " loading modules: "

# Need to verify that all modules have all required dependencies
#
echo " - Verifying that all kernel modules are ok"
$DEPMOD -a

# With the new IPTABLES code, the core MASQ functionality is now either
# modular or compiled into the kernel. This HOWTO shows ALL IPTABLES
# options as MODULES. If your kernel is compiled correctly, there is
# NO need to load the kernel modules manually.
#
# NOTE: The following items are listed ONLY for informational reasons.
# There is no reason to manual load these modules unless your
# kernel is either mis-configured or you intentionally disabled
# the kernel module autoloader.
#

# Upon the commands of starting up IP Masq on the server, the
# following kernel modules will be automatically loaded:
#
# NOTE: Only load the IP MASQ modules you need. All current IP MASQ
# modules are shown below but are commented out from loading.
# ===============================================================

echo "----------------------------------------------------------------------"

#Load the main body of the IPTABLES module - "iptable"
# - Loaded automatically when the "iptables" command is invoked
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_tables, "
$MODPROBE ip_tables


#Load the IPTABLES filtering module - "iptable_filter"
# - Loaded automatically when filter policies are activated


#Load the stateful connection tracking framework - "ip_conntrack"
#
# The conntrack module in itself does nothing without other specific
# conntrack modules being loaded afterwards such as the "ip_conntrack_ftp"
# module
#
# - This module is loaded automatically when MASQ functionality is
# enabled
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "ip_conntrack, "
$MODPROBE ip_conntrack


#Load the FTP tracking mechanism for full FTP tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_conntrack_ftp, "
$MODPROBE ip_conntrack_ftp


#Load the IRC tracking mechanism for full IRC tracking
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_conntrack_irc, "
$MODPROBE ip_conntrack_irc


#Load the general IPTABLES NAT code - "iptable_nat"
# - Loaded automatically when MASQ functionality is turned on
#
# - Loaded manually to clean up kernel auto-loading timing issues
#
echo -en "iptable_nat, "
$MODPROBE iptable_nat


#Loads the FTP NAT functionality into the core IPTABLES code
# Required to support non-PASV FTP.
#
# Enabled by default -- insert a "#" on the next line to deactivate
#
echo -en "ip_nat_ftp, "
$MODPROBE ip_nat_ftp


#Loads the IRC NAT functionality into the core IPTABLES code
# Required to support NAT of IRC DCC requests
#
# Disabled by default -- remove the "#" on the next line to activate
#
#echo -e "ip_nat_irc"
#$MODPROBE ip_nat_irc

echo "----------------------------------------------------------------------"

# Just to be complete, here is a partial list of some of the other
# IPTABLES kernel modules and their function. Please note that most
# of these modules (the ipt ones) are automatically loaded by the
# master kernel module for proper operation and don't need to be
# manually loaded.
# --------------------------------------------------------------------
#
# ip_nat_snmp_basic - this module allows for proper NATing of some
# SNMP traffic
#
# iptable_mangle - this target allows for packets to be
# manipulated for things like the TCPMSS
# option, etc.
#
# --
#
# ipt_mark - this target marks a given packet for future action.
# This automatically loads the ipt_MARK module
#
# ipt_tcpmss - this target allows to manipulate the TCP MSS
# option for braindead remote firewalls.
# This automatically loads the ipt_TCPMSS module
#
# ipt_limit - this target allows for packets to be limited to
# to many hits per sec/min/hr
#
# ipt_multiport - this match allows for targets within a range
# of port numbers vs. listing each port individually
#
# ipt_state - this match allows to catch packets with various
# IP and TCP flags set/unset
#
# ipt_unclean - this match allows to catch packets that have invalid
# IP/TCP flags set
#
# iptable_filter - this module allows for packets to be DROPped,
# REJECTed, or LOGged. This module automatically
# loads the following modules:
#
# ipt_LOG - this target allows for packets to be
# logged
#
# ipt_REJECT - this target DROPs the packet and returns
# a configurable ICMP packet back to the
# sender.
#

echo -e " Done loading modules.\n"



#CRITICAL: Enable IP forwarding since it is disabled by default since
#
# Redhat Users: you may try changing the options in
# /etc/sysconfig/network from:
#
# FORWARD_IPV4=false
# to
# FORWARD_IPV4=true
#
echo " Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward


# Dynamic IP users:
#
# If you get your IP address dynamically from SLIP, PPP, or DHCP,
# enable this following option. This enables dynamic-address hacking
# which makes the life with Diald and similar programs much easier.
#
echo " Enabling DynamicAddr.."
echo "1" > /proc/sys/net/ipv4/ip_dynaddr


# Enable simple IP forwarding and Masquerading
#
# NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
#
# NOTE #2: The following is an example for an internal LAN address in the
# 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask
# connecting to the Internet on external interface "eth0". This
# example will MASQ internal traffic out to the Internet but not
# allow non-initiated traffic into your internal network.
#
#
# ** Please change the above network numbers, subnet mask, and your
# *** Internet connection interface name to match your setup
#


#Clearing any previous configuration
#
# Unless specified, the defaults for INPUT and OUTPUT is ACCEPT
# The default for FORWARD is DROP (REJECT is not a valid policy)
#
echo " Clearing any existing rules and setting default policy.."
$IPTABLES -P INPUT ACCEPT
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -t nat -F

echo " FWD: Allow all connections OUT and only existing and related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
$IPTABLES -A FORWARD -j LOG

echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF"
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE

echo -e "\nrc.firewall-2.4 v$FWVER done.\n"

----------------------------------------------------------------------------------
Any thoughts?

Thanx

Loki
Rendai Media
 
Old 06-23-2004, 09:08 AM   #2
maxut
Senior Member
 
Registered: May 2003
Location: istanbul
Distribution: debian - redhat - others
Posts: 1,188

Rep: Reputation: 50
try www.iptables-script.dk
 
Old 06-23-2004, 10:03 AM   #3
rendaimedia
LQ Newbie
 
Registered: Apr 2004
Posts: 10

Original Poster
Rep: Reputation: 0
dont think that would work because im trying to share a ppp0 dialup connection, the ip changes each connection...

I did notice when looking over my script that:
# Dynamic IP users:
#
# If you get your IP address dynamically from SLIP, PPP, or DHCP,
# enable this following option. This enables dynamic-address hacking
# which makes the life with Diald and similar programs much easier.
#
echo " Enabling DynamicAddr.."
echo "1" > /proc/sys/net/ipv4/ip_dynaddr

I am not using dynamic ips so how do i write in the ips here? it doesn't have an example?

here:

Enable simple IP forwarding and Masquerading
#
# NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
#
# NOTE #2: The following is an example for an internal LAN address in the
# 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask
# connecting to the Internet on external interface "eth0". This
# example will MASQ internal traffic out to the Internet but not
# allow non-initiated traffic into your internal network.
#
#
# ** Please change the above network numbers, subnet mask, and your
# *** Internet connection interface name to match your setup

My server is 10.10.1.1
subnet 255.255.255.0
network 10.10.1.0
etc etc

So basically want to access ppp0 (dial up) through 10.10.1.1 yeah?
 
Old 06-23-2004, 10:32 AM   #4
rendaimedia
LQ Newbie
 
Registered: Apr 2004
Posts: 10

Original Poster
Rep: Reputation: 0
Also apart from the dynamic address thing stuffing it up i get this output from the script:

Loading simple rc.firewall version 0.75..

External Interface: ppp0
Internal Interface: eth0
loading modules: - Verifying that all kernel modules are ok
----------------------------------------------------------------------
ip_tables, ip_conntrack, ip_conntrack_ftp, ip_conntrack_irc, iptable_nat, ip_nat_ftp, ----------------------------------------------------------------------
Done loading modules.

Enabling forwarding..
Enabling DynamicAddr..
Clearing any existing rules and setting default policy..
/etc/rc.d/rc.firewall-2.4: line 282: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 283: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 284: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 285: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 286: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 287: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 288: /usr/local/sbin/iptables: No such file or directory
FWD: Allow all connections OUT and only existing and related ones IN
/etc/rc.d/rc.firewall-2.4: line 291: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 292: /usr/local/sbin/iptables: No such file or directory
/etc/rc.d/rc.firewall-2.4: line 293: /usr/local/sbin/iptables: No such file or directory
Enabling SNAT (MASQUERADE) functionality on ppp0
/etc/rc.d/rc.firewall-2.4: line 296: /usr/local/sbin/iptables: No such file or directory

rc.firewall-2.4 v0.75 done.

Does anyone know how to fix this??

Ta
Loki
 
Old 06-23-2004, 10:43 AM   #5
rendaimedia
LQ Newbie
 
Registered: Apr 2004
Posts: 10

Original Poster
Rep: Reputation: 0
ive now fixed the bad link to iptables so thats all good but need to know how to structure this bit:

Enable simple IP forwarding and Masquerading
#
# NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
#
# NOTE #2: The following is an example for an internal LAN address in the
# 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask
# connecting to the Internet on external interface "eth0". This
# example will MASQ internal traffic out to the Internet but not
# allow non-initiated traffic into your internal network.
#
10.10.1.0
# ** Please change the above network numbers, subnet mask, and your
# *** Internet connection interface name to match your setup

at the moment i have 10.10.1.0 there to see if that'll do it but no go...

??????
 
Old 06-23-2004, 10:55 AM   #6
rendaimedia
LQ Newbie
 
Registered: Apr 2004
Posts: 10

Original Poster
Rep: Reputation: 0
All good guys, I #'d out the dynamic bit and put in 10.10.1.0/255.255.255.0 and 'It's Alive!"
 
  


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