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The Answer Guy

By James T. Dennis, tag@lists.linuxgazette.net
Starshine Technical Services, http://www.starshine.org/

Network Cards

From Greg on 04 May 1998

Hey there,

I recently purchased a copy of Redhat 5 and installed it on a system. My intentions for this system was for it to act as a proxy server and a mail server. I used a machine I had spare and installed. All of the devices detected but now I can't seem to get my network card to act. I checked the network settings in netcfg in xwindows but it said that the card was active. The card isn't responding (according to the lights) though. I have now tried two cards (3com 10/100 mb and a kingston 10 mb) and both have returned the same error on pinging an address (Network is unreachable.)

Here's a synopsis of configuring a system for ethernet networking under Linux:

load modules (if necessary)

They may be built directly into your kernel.

ifconfig $IF $IPADDR $NETMASK $BCAST

If you get an error like:
SIOCSIFADDR: No such device
go back and load the correct driver or compile it into your kernel. If you still get that error it's probably an unsupported card --- or you're trying to use the wrong driver.

route add -net $NET $IF

Add an entry to the kernel's routing table to associate your LAN with that interface.

route add default gw $ROUTER (if necessary)

Add a route to point to your LAN's router to the "rest" of the world. Note, in some cases you might not define a default route. For example if your box is the router between your LAN and an ISP that you dial up with PPP or diald. (In that case the default route would be set by your pppd and diald packages whenever the link to your ISP became active).

Is there something else I have to initialise to get my cards to work or do you think it could be a conflict of sorts?

When trying to troubleshoot networking problems the commands you want to beat on are:

ifconfig -a	list all interfaces
route -n	list all defined routes
ping	try to reach various hosts
tcpdump -i $IF -vvv	dump all activity occuring on an interface
traceroute	watch how packets "try" to reach their destinations

In this case you want to post the output of your 'ifconfig -a' and 'route -n' commands as well as the IP address and network/mask that you're attempting to use (for each interface).

Note: since you mention that you're trying to configure this system as a proxy server it's important that you get each of of its interfaces working properly before attempting to use any routing, masquerading or proxying through it.

What proxy package(s) are you trying to use?

Thanks
Greg!

You're welcome.

Copyright © 1998, James T. Dennis
Published in Linux Gazette Issue 29 June 1998

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