network printer changes IP address

[Relztrah]

This isn't really a problem and our printer works fine from several workstations. I'm just curious why every time I set up a new workstation and install our HP 2600n network printer, it has a different IP address. Sometimes it's 192.168.1.121, sometimes 192.168.1.114, or 192.168.1.110, and it seems to change every time. The printer is connected directly to a switch which is connected to our router, all with Ethernet cables, nothing wireless. So why does the IP address change?

[Rick]

The printer will only hold it's address as long as it is turned on

If you turn it off
Then boot another system
The router can and will assign it's address to the new system booted

You can assign the addresses yourself .
Locking them and turning off the auto feature of your router(DHCP) (http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol)

[Relztrah]

As long as the printer is working OK, I see no reason to give it a fixed IP address. Why, then, doesn't my PC (or any of them on the network) also change its IP address when I reboot?

[Sun-Tzu]

Good question,

It all depends how your router is set up and what devices are turned on when.

Bottom line is that you actually only have one "real" IP address and your router adds a mask to that in order to create more IPs for your Local LAN. The way that these IPs are given out depends on your particular router.

And you're right, there is no real reason to give your devices static IPs in a home situation.

[Variable]

Bottom line is that you actually only have one "real" IP address and your router adds a mask to that in order to create more IPs for your Local LAN


...huh?

--------------------------------------------------------------------------

As for the printer problem..



If your printer is set to DHCP it should get it's lease parameters from the DHCP server. If your DHCP server is your router, your lease time dictates how long the router will allow a machine to keep an IP address. It will keep a table of MAC addresses and IP addresses assigned to those MAC addresses and will also keep a lease period for each. If a machine is set to "Obtain IP address automatically" in the network properties of the network card and it reboots, when it reboots it may try to obtain a new IP address from the DHCP server, if the DHCP server already has this machines MAC address in it's lease table and the lease has not expired... then it should try to give the SAME ip address it has in it's table. The machine can accept or reject this IP address. It could be that your printer rejects the IP address for some reason and gets a different IP. The DHCP server then updates it's lease table.

So assume your lease range is 24 hours. You boot a PC up, it gets an IP address and then after 6 hours you reboot again. The IP address lease time has not expired, it should get the same IP address again.

Assume the above scenario but now we boot up your printer. It should behave exactly as the PC above. It is could be that it does not accept the same IP again after a reboot and requests a different IP.

[Erik]

As long as the printer is working OK, I see no reason to give it a fixed IP address. Why, then, doesn't my PC (or any of them on the network) also change its IP address when I reboot?

Why not give it a static IP? It is easy to do, and then you will always know what IP the printer is. Just set it to something outside of the DHCP scope (say 192.168.1.200) and everything will be fine.

One good reason for this is if you ever want to visit the web admin page you know what IP to go to.