[aclug-L] IP Forwarding

[Glen Diener <glen@xxxxxxxxxxxxxxxx>]

Im attempting to use a Linux (Caldera OpenLinux) box  as a firewall which
forwards IP packets from one network to another.  I have two working
network cards installed in the server and have recompiled, according to
the Linux howto pages, the kernel to include the necessary features for IP
forwarding/masquerading.  Both sides of the firewall can ping the IP
number of the network card which is directly attached, but, neither side
can ping the IP numbers on the other network.  My configuration is as
follows:

[root@bilbo glen]# ifconfig
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Bcast:127.255.255.255  Mask:255.0.0.0
          UP BROADCAST LOOPBACK RUNNING  MTU:3584  Metric:1
          RX packets:61 errors:0 dropped:0 overruns:0
          TX packets:61 errors:0 dropped:0 overruns:0

eth0      Link encap:Ethernet  HWaddr 00:A0:C9:71:53:FF
          inet addr:198.248.166.17  Bcast:198.248.166.255
Mask:255.255.255.0
          IPX/Ethernet 802.2 addr:00A0C97153FF
          IPX/Ethernet 802.3 addr:00000501:00A0C97153FF
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:171530 errors:0 dropped:0 overruns:0
          TX packets:7248 errors:0 dropped:0 overruns:0
          Interrupt:5 Base address:0xe400

eth1      Link encap:Ethernet  HWaddr 00:A0:C9:71:53:FE
          inet addr:192.168.2.1  Bcast:192.168.2.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:202 errors:0 dropped:0 overruns:0
          TX packets:119 errors:0 dropped:0 overruns:1
          Interrupt:9 Base address:0xe800

[root@bilbo glen]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
255.255.255.255 0.0.0.0         255.255.255.255 UH    0      0        0
eth0
198.248.166.0   0.0.0.0         255.255.255.0   U     0      0       21
eth0
192.168.2.0     0.0.0.0         255.255.255.0   U     0      0        3
eth1
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        5 lo
0.0.0.0         198.248.166.254 0.0.0.0         UG    1      0        5
eth0
[root@bilbo glen]#


The ipfwadm commands I've used are those given in the IP Masquerading
howto page. 

        ipfwadm -F -p deny 
       ipfwadm -F -a m -S 192.168.1.0/24 -D 0.0.0.0/0 

Any suggestions on why this doesn't work or how I can diagnose the
problem? 


Glen Diener
Tabor College
glen@xxxxxxxxxxxxxxxx

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