Category: Unix/Linux

I had a call a couple of days ago from a company planning to sell some networked printers to a user site I oversee. The first I heard about it was a form from the supplier asking a few questions about the network; questions that suggested they expect to find a Microsoft small office plug and play kind of LAN. Time to get on the blower.

The question that worried me most was their demand for a static IP address, subnet mask and so on. Not happening; everything is on DHCP and managed centrally, for good reason. Kit like printers needs to auto-configure to the correct subnet depending on where it’s plugged in, and users will expect it to work. So why is anyone thinking of hard configuring the IP address at the printer?

The simple answer is that it’s the easy way, and in the bad old days, it was the norm. It may even be necessary on a network controlled by a crude domestic router with a DHCP server that can be configured to either be “on” or “off”. If you’re using from a Windows PC you need to set up a virtual printer port, and to do this you must supply the IP address of the physical printer, so just set a static one and plug this in when the driver configurations asks for it. Simple. If you’re Fred in a Shed, with two PCs and one shared printer.

If you’re playing with the big boys, you’re creating a world of pain by hard configuring printers, as you have to manually reconfigure each printer and EVERY PC in the company when you move it around on the LAN.

So what should you be doing instead? If your company (and/or its budget) is large enough you can get a point+click print server to manage the whole lot. I’ve found these a bit vendor-specific, and only really do it if you have a Wizard that understands all your printers and the LAN. Otherwise you’re going to have to get your hands dirty anyway. So for a SME, with a savvie IT guy, there are two simple approaches that achieve the results you need without the fuss: NetBIOS and DNS. Leave the network printers stand-alone, as nature intended.

The easy option with Windows PCs is to use the NetBIOS name. Most fancy printers have one, and it’s usually programmable if you dig around in the menus. It can sometimes be hard to recognise as it defaults to something akin to gibberish. You also have to enable NetBIOS on the printer if necessary, although in my experience most enable every protocol they know about by default. Once done, just use the NetBIOS name instead of he IP address in the virtual printer driver and you’re away – nothing more to do. The down side is that not everything understands NetBIOS/SMB/CFIS, although most UNIX systems can resolve them using SAMBA if necessary. And to be honest, Microsoft’s self-configuring peer-to-peer networking has always been a bit hit and miss. (Luser: “I can’t see xxxx!”)

A more complete solution is to use DNS. This obviously means you’re going to need a local DNS server, and also a proper DHCP server. If you want to get clever, have the DHCP server update the DNS with the host name associated with the IP addresses it’s just given out. This works in theory, but good luck in practice. However, there’s an easier way that is almost as good.

All you need to do is configure the DHCP server to issue fixed IP addresses when it gets a request from the MAC addresses of each of your printers. On GUI based DHCP servers this is often called “Bind IP to MAC” or similar. On dhcpd you just need a specific entry in the config file, such as:

host bigprinter1 {
hardware ethernet 11:22:33:44:55:66;
fixed-address 192.168.1.123;
}

Okay, this is giving it a fixed address, but all the fixed addresses are found in one file, along with the other network configuration stuff, and you don’t need to trail around to each printer (or even visit the site) to change it. And besides, this is never referenced in the printer or any of the workstations; they use a symbolic name.

To achieve this you need to add an A record for the printer at this address in your DNS zone file. e.g.:

You don’t even need to use on-site DNS if you have a reliable Internet connection (or your domestic router has a caching DNS relay). Just go to the easy peasy web configuration thingy for your outside-hosted domain and add it. The fact that its a local, non-routing IP address won’t matter – people outside the building just won’t get what they’re expecting if they try to use it, but they shouldn’t be doing this anyway.

As a final point, it’s safer to make sure the NetBIOS name and the DNS hostname match, but its not essential.

Whichever method you use for the name lookup, just plug the NetBIOS name or DNS hostname in to the printer driver instead of a fixed IP address and you’ll never have to physically mess with the printer again – wherever the users choose to plug it in.