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Old 08-01-2004, 11:15 PM   #1
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Location: Australia
Distribution: Linux From Scratch, Debian Woody & Sarge
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Strange networking problem

Hi, I'm having a very strange networking problem that has my linux
buddies and I stumped.

I'll draw a basic mud map because it makes it ALOT easier to understand
my situation as I have two gateways due to shared housing.

        [Bridged ADSL Modem]
    |                     |
  [DMZ]     [Workstations] and [my Debian Box]
(10.0.1.*)    (10.0.0.*)    (,
                              [my workstation]
Last week my Debian Box had a hard shutdown due to a knocked out
powercable and when I rebooted it could no access the internet, other workstations, firewall or DMZ. And neither could my Workstation. The
weird thing is, that all the above mentioned machines, can still contact
my Debian Box. eg: The Firewall can ping my Debian Box, but my Debian
Box can't ping the firewall. My Debian Box is hosting some friends
websites and hosts some email accounts, which all still work. From my
workstation I can ping my Debian Box and It can ping me, but in order
for me to get on the net with my workstation, ive had to plug in with
the rest of the workstations (ie: not go through my Debian Box)

I have flushed all iptables rules and set policies to ACCEPT so it is
not a firewall problem. I have tried 4 other NIC's and even put the hard drive in another box so it is not a hardware problem. I have also tried switching the IP's of eth0 and eth1 around and even set eth0 to use DHCP (provided by the Firewall)

*[root@holly:~] cat /proc/sys/net/ipv4/ip_forward
*[root@holly:~] route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface   U     0      0        0 eth0   U     0      0        0 eth1         UG    0      0        0 eth0
It's obviously not extra urgent because people can still access their websites and emails from the outside, It's just a pain. I can't even do an 'apt-get upgrade' in the hope of overwritting whatever it stuffing this up.

Hope i've provided enough information and thanks for any help.

- jrb
Old 08-02-2004, 12:35 AM   #2
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Location: CA
Distribution: openSuSE, Cent OS, Slackware
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Did you replace the Ethernet cable? They do go bad.
Old 08-02-2004, 01:30 AM   #3
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Registered: Aug 2004
Location: Australia
Distribution: Linux From Scratch, Debian Woody & Sarge
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Thanks for the reply. Yes, I have tried changing the cable plugged into the NIC and the cable at the patch panel.. The only one i cant change is the one going through the wall but all 4 pairs are still intact. I have also tried changing the switch and as mentioned before the NIC's and even the entire box. The only thing that i havent changed is the hard drive. My workstation is also unaffected using the same cable.


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