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Old 12-01-2003, 09:51 PM   #1
LQ Newbie
Registered: Nov 2003
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2 nic router problem

I am a newby working on implementing a Linux router as part of a small network. The network consists of:

· hosts which are set at [192.168.48.xx];
· the router with an internal nic card [eth1 at] and an external nic card [eth 0 at].
· The router is a RedHat 7.3 machine running the 2.4.7 kernal.
· The default gateway for eth0 is
· IPChains is disabled
· IPTables is automatic
· Firewall is disabled [for now]
· /etc/sysctl.conf has the line “net.ipv4.ip_forward=1”
· Routes that have been entered are:

Gateway netmask Network

We can ping the default gateway from router eth0.

We can ping the router eth0 from the hosts.

We can ping the router eth1 from the hosts.

We have been unable to ping the default gateway from the hosts.

We have been unable to ping from eth0 to eth1

Thanks to all. This forum has been a great deal of help.

Old 12-01-2003, 10:09 PM   #2
Senior Member
Registered: Jul 2003
Location: Silicon Valley, USA
Distribution: OpenBSD 4.6, OS X 10.6.2, CentOS 4 & 5
Posts: 3,660

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You've made a classic networking blunder. Each NIC needs to be on it's own subnet. The ip_forward setting will take care of making packets go where they're supposed to, you don't have to "point" the interfaces at each other.

Reconfigure as such:
eth0 =
eth1 =
Old 12-04-2003, 10:32 PM   #3
LQ Newbie
Registered: Nov 2003
Posts: 2

Original Poster
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2 nic router problem


Linux routing is alive and well. Thanks for the assistance.



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