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(OT): networking problem (using Sarge as router)


This is a bit off topic, but since it involves Knoppix and Sarge network interfaces files, I thought maybe I could get some help here.

I am trying to add another computer to my internal home network. My main computer, say HomeR (running Debian Sarge 2.4.24-1-686), working as a router has two NICs. It's eth0 connects to the high speed modem and eth1 connects to a switch and has the configuration:
#> cat /etc/network/interfaces
# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
# /usr/share/doc/ifupdown/examples for more information.
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
auto lo
iface lo inet loopback

# The first network card - this entry was created during the Debian installation
# (network, broadcast and gateway are optional)
auto eth0
iface eth0 inet static
#        gateway
        pre-up /etc/iptables/iptables.sh panic
        pre-up /etc/iptables/iptables.sh preup_start
auto eth1
iface eth1 inet static
#        gateway
The route command on HomeR gives:
#> route -n
Kernel IP routing table
Destination    Gateway        Genmask         Flags Metric Ref    Use Iface
a.b.c.d UH    0      0        0 ppp0   U     0      0        0 eth0   U     0      0        0 eth1        a.b.c.d         UG    0      0        0 ppp0

where a.b.c.d is the IP that my ISP provides each time I connect to it.

My two internal computer are connected to the swith from their NICs.

One of my internal home computers, say Home1, is and is working fine (ping, internet, ssh, etc. towards HomeR and outside). The other, say Home2, is the one I am trying to add. I put in Knoppix and set Home2 up as, with netmask, gateway and with the nameserves which are listed in /etc/resolve.conf of HomeR (the router machine).

I cannot ping to or from any other computer. Domain names do not get resolved. If I try pinging it from HomeR, I get:
# ping -c4
PING ( 56(84) bytes of data.
From icmp_seq=1 Destination Host Unreachable
From icmp_seq=2 Destination Host Unreachable
From icmp_seq=3 Destination Host Unreachable
From icmp_seq=4 Destination Host Unreachable

--- ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3000ms
, pipe 3

But if I disconnect Home1 from the internal LAN, and do 'tcpdump -i eth1' on HomeR, and ping HomeR from Home2, I get:
# tcpdump -i eth1
tcpdump: listening on eth1
03:19:03.838878 arp who-has tell
03:19:03.838928 arp reply is-at 0:50:ba:50:3:87
03:19:04.833008 arp who-has tell
03:19:04.833039 arp reply is-at 0:50:ba:50:3:87
03:19:05.833046 arp who-has tell
03:19:05.833091 arp reply is-at 0:50:ba:50:3:87

But if I do 'tcpdump -i eth0' on Home2 and ping Home2 from HomeR, I get no activity. So it seems that Home2 is able to send packets to the network, but no other machine is able to send any to

Any ideas what could be going wrong or how do I go about solving this?

Thanks a ton,

(Remove all underscores,_if any_, from my email address to get the correct one. Apologies for the inconvenience, but this is to reduce spam.)

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