Router with only one interface [SOLVED]

Toris · n00b Joined: 22 Mar 2004 Posts: 58

Hi,

This is probably an unusual question, but would it be possible to build a broadband (2mbit) router on a PC with only one ethernet port? The modem is also ethernet.

Basically I was planning on having the modem send all data to the linux router, then the linux router act as a firewall/router/server to the other PCs on the network.

To me it seems as if it will work, as the ethernet port shouldn't be saturated with only 2mbit running through a 100mbit lan... but if anyone can say any reasons why it wouldn't work/is a bad idea, I'd like to know! :oops:

Cheers!

sandcrawler · Posted: Wed Jan 04, 2006 2:28 am Post subject:

It'll work,but the reason it's a bad idea is that the internal machines aren't really separated from the outside world. If the modem is dhcping the ip address to the client then anything on that hub/switch that also dhcps might snatch the IP address. Unless you trust everyone on your network they could also sniff and get the ip address and possibly bypass your router.

My suggestion would be to get the cheapest nic you can find, probably less than $15, and toss it in there. You probably know someone that will give ya one if ya ask around.
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sandcrawler

Toris · n00b Joined: 22 Mar 2004 Posts: 58

I probably should have mentioned in the first post that the system is a Mini-ITX board, and so only has 1 PCI slot. Security isn't really an issue internally, since it's just a family network, nothing of any huge importance.

However, since the PCI slot isn't used for anything else at present, I do have a spare PCI network card available, so I can use that for the time being. I guess my two options for the future are either use a USB ethernet adapter for connecting to the ethernet modem, or remove the ethernet modem and use a direct USB connection, any comments as to which you believe would be better? (The ethernet modem does have a pretty decent firewall ruleset, so that may be of use later on).

Thanks for your reply

arkepp · Posted: Wed Jan 04, 2006 10:09 pm Post subject:

The USB interface to many of the modems (at least Motorolas) is significantly slower. I have never used USB Ethernet adapters, but my guess would be that the driver would required a lot of CPU time. The latter is probably still better, but the former is free to try.

sandcrawler · Posted: Wed Jan 11, 2006 4:41 am Post subject:

I see how one pci slot can be a problem

You could try it USB, but it would be slower like the previous post explained, and probably buggy too.

If possible set the router not to dhcp anything internally and let your box worry about internal DHCP. Set the routers internal address on a different subnet to keep broadcasts and other junk traffic separated somewhat, and go from there.
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sandcrawler