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    I am trying to set up IP Masqing, and I can't get past step 3 of the
troubleshooting part of the HOWTO. I have two machines. I am running
redhat linux 6.2 w/kernel 2.2.16 installed on both boxes. I have
recompiled the kerenel with the correct settings. One is the masq
server(snarf) with two internet cards. eth0 is the outside interface. It
is configured using DHCP, and it works. (I can access the internet with
it.) eth1 is the interface to the internal server. It has an IP of
192.168.0.1 and 255.255.255.0 as subnet. I can ping 192.168.0.1 (eth1)
from snarf with no problem. The Masq'ed machine (orko) has an IP of
192.168.0.2 and a subnet of 255.255.255.0. From orko, I can ping
192.168.0.2 (it's own interface.) I cannot, however, get orko or snarf
to ping each other. I checked the configurations of orko and snarf as
the HOWTO said, but they seem to be correct.
    There is a link between the computers. (The NICs and the switch all
have lights on.) I checked the archives and someone reccomended using a
crossover cable, but I don't think this is necessary when they are
connected with a switch. There is nothing wrong with the cables or the
cards. I have used all of them to access the internet. All the
information is below. Sorry if this has been answered before, but I
could not find it in the archives. Also, I'm sorry for the long e-mail,
but I should probably give you all the info or you won't be able to help
me.

Thanks in advance.
Arun

internal MASQ'ed computer(orko):

[root@orko /root]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:10:5A:27:35:13
          inet addr:192.168.0.2  Bcast:192.168.0.255  Mask:255.255.255.0

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:23431 dropped:0 overruns:4 frame:35967
          TX packets:96 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:11 Base address:0x1000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:3924  Metric:1
          RX packets:52 errors:0 dropped:0 overruns:0 frame:0
          TX packets:52 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0

MASQ server(snarf):

[root@snarf /root]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:DA:CE:FC:76
          inet addr:64.192.48.165  Bcast:64.192.48.167
Mask:255.255.255.252
          UP BROADCAST RUNNING  MTU:1500  Metric:1
          RX packets:105 errors:0 dropped:0 overruns:0 frame:0
          TX packets:120 errors:0 dropped:0 overruns:0 carrier:4
          collisions:0 txqueuelen:100
          Interrupt:11 Base address:0xdc80

eth1      Link encap:Ethernet  HWaddr 00:50:DA:8A:B9:AD
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:205 errors:0 dropped:0 overruns:0 frame:0
          TX packets:90 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:10 Base address:0xdc00

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:3924  Metric:1
          RX packets:19 errors:0 dropped:0 overruns:0 frame:0
          TX packets:19 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0

[root@snarf /root]# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask             Flags   MSS Window
irtt Iface
192.168.0.1     0.0.0.0         255.255.255.255     UH        0
0          0 eth1
64.192.48.164   0.0.0.0         255.255.255.252     U         0
0          0 eth0
192.168.0.0         0.0.0.0         255.255.255.0       U         0
0          0 eth1
127.0.0.0                 0.0.0.0         255.0.0.0           U
0 0          0 lo
0.0.0.0               64.192.48.166   0.0.0.0             UG        0
0          0 eth0

[root@snarf /root]# cat /proc/sys/net/ipv4/ip_forward
1

[root@snarf /root]# ipchains -M -L
IP masquerading entries

My firewall script is below. It is the one from the IP-MASQ HOWTO
website with a few changes.

#!/bin/sh
#
# rc.firewall - Initial SIMPLE IP Masquerade test for 2.1.x and 2.2.x
kernels using IPCHAINS
#
# Load all required IP MASQ modules
#
#   NOTE:  Only load the IP MASQ modules you need.  All current IP MASQ
modules
#          are shown below but are commented out from loading.

# Needed to initially load modules
#
/sbin/depmod -a

# Supports the proper masquerading of FTP file transfers using the PORT
method
#
#/sbin/modprobe ip_masq_ftp

# Supports the masquerading of RealAudio over UDP.  Without this module,

#       RealAudio WILL function but in TCP mode.  This can cause a
reduction
#       in sound quality
#
#/sbin/modprobe ip_masq_raudio

# Supports the masquerading of IRC DCC file transfers
#
#/sbin/modprobe ip_masq_irc


# Supports the masquerading of Quake and QuakeWorld by default.  This
modules is
#   for for multiple users behind the Linux MASQ server.  If you are
going to play
#   Quake I, II, and III, use the second example.
#
#   NOTE:  If you get ERRORs loading the QUAKE module, you are running
an old
#   -----  kernel that has bugs in it.  Please upgrade to the newest
kernel.
#
#Quake I / QuakeWorld (ports 26000 and 27000)
#/sbin/modprobe ip_masq_quake
#
#Quake I/II/III / QuakeWorld (ports 26000, 27000, 27910, 27960)
#/sbin/modprobe ip_masq_quake 26000,27000,27910,27960


# Supports the masquerading of the CuSeeme video conferencing software
#
#/sbin/modprobe ip_masq_cuseeme

#Supports the masquerading of the VDO-live video conferencing software
#
#/sbin/modprobe ip_masq_vdolive


#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 "1" > /proc/sys/net/ipv4/ip_forward


#CRITICAL:  Enable automatic IP defragmenting since it is disabled by
default in 2.2.x kernels
#
#           This used to be a compile-time option but the behavior was
changed in 2.2.12
#
echo "1" > /proc/sys/net/ipv4/ip_always_defrag


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


# Enable the LooseUDP patch which some Internet-based games require
#
#  If you are trying to get an Internet game to work through your IP
MASQ box,
#  and you have set it up to the best of your ability without it
working, try
#  enabling this option (delete the "#" character).  This option is
disabled
#  by default due to possible internal machine UDP port scanning
#  vunerabilities.
#
#echo "1" > /proc/sys/net/ipv4/ip_masq_udp_dloose


# MASQ timeouts
#
#   2 hrs timeout for TCP session timeouts
#  10 sec timeout for traffic after the TCP/IP "FIN" packet is received
#  160 sec timeout for UDP traffic (Important for MASQ'ed ICQ users)
#
/sbin/ipchains -M -S 7200 10 160


# DHCP:  For people who receive their external IP address from either
DHCP or BOOTP
#        such as ADSL or Cablemodem users, it is necessary to use the
following
#        before the deny command.  The "bootp_client_net_if_name" should
be replaced
#        the name of the link that the DHCP/BOOTP server will put an
address on to?
#        This will be something like "eth0", "eth1", etc.
#
#        This example is currently commented out.
#
#
/sbin/ipchains -A input -j ACCEPT -i eth0 -s 0/0 67 -d 0/0 68 -p udp

# Enable simple IP forwarding and Masquerading
#
#  NOTE:  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.
#
#         Please change this network number and subnet mask to match
your internal LAN setup
#
/sbin/ipchains -P forward DENY
/sbin/ipchains -A forward -s 192.168.0.0/24 -j MASQ

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