Can Old Laptops Be Routers Too?

Porthos writes "There are several HOWTOs about installing Linux on laptops and several more about turning old P75s into Linux-based routers/firewalls, but I haven't heard much about turning old P75 laptops into Linux-based routers." Is there any reason to disrecommend a laptop as a router? I know people with their old portables running as servers, routers, and everything else ...

"As best as I can tell, an old laptop would make a perfect Linux router. You have a notebook-sized machine that has it's own monitor, mouse, and keyboard that easily hide away when the machine is not in need of human attention. Furthermore, most laptops have two PCMCIA slots to accommodate the two necessary network cards. My old WinBook XP even has a built in modem for dial-in access, should the situation demand it.

If the power goes out, a notebook computer would keep running for anywhere from 30 minutes to two hours. This would allow any critical systems to complete their tasks, assuming that they are on a UPS. And if you need to use such a setup at an alternate location, you could just pickup and go with the laptop.

My question is this: Is there a downside to using an old laptop as a Linux-based router? Obviously you wouldn't use such a device in a large-scale office setting, but could this be a viable alternative to picking up one of those $130 Linksys Cable/DSL routers? If not, why not?"

Comments

Use a 486 laptop

[Cato]

I have an old Thinkpad 486/75 laptop, and it works fine as a Linux router/firewall. For a long time I had one ethernet card and one modem card (left over from when it was used as a laptop). I then bought another ethernet card to talk to an ADSL/ethernet router - it has no problem working at 1 Mbps and could probably go faster (many low end Cisco routers are very low powered).

It's more hassle than a dedicated firewall box to set up, but it's cheaper and I really couldn't use a 640x480 screen laptop for anything else these days. Most importantly, it's very flexible - I can write my own script to analyse logs, install extra tools for intrusion detection, and so on.

The biggest pain is trying to get OpenBSD to work with PCMCIA cards - haven't yet managed to get this working, so if you want OpenBSD you may be better off with a desktop/tower type PC.

Heat, cost and expandability

[Bryan Andersen]

Heat: As others have mentioned, laptops run hot.

Cost: An old laptop is still worth alot more than an old PC from the same era. Old P75 computers are dirt cheep. Usually $50 or less, please, please take them off our hands.

Expandability: A laptop usually has at most 2 slots for expansion. That's it. An old P75 will likely have 3 PCI slots plus 3-4 ISA slots. This allows it to be a firewall for both a local network as well as a DMZ, and have each segment physically separate. I evicted the PCI graphics card from my firewall and replaced it with an old ISA VGA card so I could use the PCI slot for a NIC. I have three PCI 10/100 NICs in it as well as a PCI SCSI card for the logging hard disks.

10base PC Cards are cheaper now

[Raetsel]

I can find 3Com 3c589c ethernet cards on Pricewatch's 'Not Exactly New' section for ~$30. (That includes a dongle)

The newer 3c589d versions (which I use around the house -- I even have spares for laptop-owning friends!) are even less expensive. $18 from a place in Texas. Again, these include dongles -- an important distinction, as you can get bare cards for about $12. (But not, apparently, from places listed with Pricewatch)

Pricewatch can be a pain with all the frames, so...

• This is the search I ran

You should be looking at what I saw -- or hopefully something even better.

This being said, I find the laptop solution to a firewall to be ideal. I have a P233 ThinkPad that OpenBSD 2.8 installed on flawlessly, and the two previously mentioned PC Cards work with equal ease. Should I need a LAN elsewhere (where there is no cable modem or xDSL), all I need do is swap the lower ethernet card for a modem. The system runs IPF in stateful mode, DHCP server on ep1 (internal interface) only (of course), no X, and SSH allowing internal (listen address 10.0.0.1) access only.

It makes for quite an impressive tool -- it's interesting to see all the scans that get /dev/null-ed, too. That, and all the ICMP from caida.org.

The final thing -- it's silent, or nearly so. My previous firewall box was a P-100 with fans and noisy hard drives. It wasn't welcome in the living room where the cable comes into the house. I don't even notice the laptop, and it fits just like a book in the bookcase. Convenient! Add a small hub, or a 10/100 switch, and your private LAN party has internet access!

Actually, yes

[bconway]

I was using an old TI P75 laptop as a masquerading gateway for my home LAN for a while when I was first learning Linux's masquerading, and while it is nice to have something that will last through a power outage, there is a problem: EXCESSIVE HEAT. Newer laptops are built a lot better these days, but the laptops you'd be looking at to use for gateways get a little too hot for my liking, with or without the screen closed. I lost one 1GB hard drive due to the excessive heat generated from a laptop running 24/7 (it was very hot to the touch), and it was not an experience I would like to repeat. Your mileage will vary greatly, of course.