Equipment Support > Hardware By Brand > D-Link > Locking IP address in Router for printer

reply to No_Strings

Re: Locking IP address in Router for printer

Given all of that, just use the static IP setup on the printer.

You'll need the IP address, subnet, gateway and DNS servers.
IP - you decide. Sounds like 192.168.1.3 or thereabouts.
Subnet - 255.255.255.0
Gateway - 192.168.1.1
DNS - get those from your ISP, by looking at the router config or by running the commands "ping ns1" and "ping ns2".

That is probably what I will do.

And it has already filled in the subnet mask and gateway from what it get from the router. Just need to lock those in and lock in the TCP/IP address.

Now on the advance page they offer DNS Sever method of either static or auto and it is set to auto.

And the primary and secondary DNS is set to the router gateway. Not sure if that is right or not.

But I really don't seen need for the DNS any way. The printer does not have to reach out to anything outside the local net.

And AFAIK all of the communication between the printer and computer are down by IP number. In fact if they used names and had a real DNS server then it would be the servers business of tracking the IP changes and I and would not be having this problem or looking at how to "fix" the DNS servers.

But I know enough to know that I don't really understand this. So I am going to google the other options just to get a little more background into what there are.

But I would still like to understand what would happen if I turned off the DHCP server in the router.

You're right on the DNS for the printer, so you understand it better than you think.

What happens when you turn off the DHCP server:
(Simplified and mutilated)

A device set to obtain an IP address automatically sends out an announcement, asking if there are any DHCP servers within earshot willing to lend a poor NIC an IP address for a bit.

The DHCP server, upon hearing the request, takes pity on the poor network device and dispenses the next available address according to the parameters in its configuration. It knows to start at a certain IP address and to only give out a set number based on those settings.

If there's no DHCP server on the network, the pleas of the desperate NIC go unheeded and the device driver will time out. A temporary IP will be assigned - 169.x.x.x. The device will not be able to connect to other devices on the network.

If all devices on the network have statically assigned TCP/IP parameters, they will not cry out for help in obtaining one and will operate in the absence of a DHCP server.

Well right now the router DHCP server is set to the default range of issuing address in the .2 to .254 range.

And I am going to have to change one end of the other to give at least one address that the router willl not assign and put the printer on that.

I guess I could put the printer at the high end expecting that the router will never get that high, but if I did some fluke it would try to assign address that high and have a conflict.

But I have noticed some strange things on the router. One of the status displays list the DHCP address and devices it has assigned.

But often it will not show all of then, although the devices are communicating OK.

My speculation is that the device already have an IP assinged to them when the router is rebooted they talk fine with that IP and don't have to ask the DHCP server for one until either the lease expires or the device is rebooted.

And at first I was thinking that the router might send out a broadcast asking who was their already or sending out a "every one shut up and ask for a new address". But that is not a guarantee either. If a device is powered up, but in a sleep mode it won't respond, but will keep it's last IP.

So I am guessing the router has some mechanism to where if it starts seening the same IP on 2 ports that it tells both of them to shut and ask for a new IP.

Although I suspect that the router has to keep a table of what IP traffic is on each port so that it knows how to route the traffic even if it did not assign the IP. And that the DHCP server is a separate function and the status only shows what the server did and not the internal tables.

Tomorrow I am going to run some 'spriment' with rebooting the router both with the other device in standby or disconnected and with the off and reboot after the router reboots and then just connecting with the laptop and seeing what it the router assigns.

BTW, the router has to have some limits on the number of ports that it can that it can route. Of course it only has 4 hardwired ports, but it can have any number of wireless connections at any one time.

While it could be setup to support the full range of .2 to .254 that seems like a lot. And I am not about the basic home level cheapest routers. I am if you have any idea of how many different connection that they will support at any one time.

Not that I really need to know, but just interested.

Thanks for the help that you have given me already.

The theoretical limit is 255, based on available addresses. The practical limit varies. If you have a slow connection and heavy downloaders, they'll be hating life it there are only a couple. Light browsing and email - 20 would play together nicely on a fast pipe.

Good luck with it.

I found a website that at a FAQ on DHCP and it was at just the right level and that help.

It did not say, but implied that the DHCP server should be able to detect conflicts and resolve them. But at least this router/DHCP server count not.

I turned off the wireless port on the laptop and unplug the printer and desktop and rebooted the router.

Then connected the router via cable to the laptop and opened that connection and got a .2 assignement for the lap top.

Then connected the printer and could not access it. Cycled power on the printer and it forced a DHCP request and got assigned to .3

Then I could access the printer webpage using .3 from the laptop.2

The reconnected the desktop that has been assigned .3 and thought that it was still on it .3

Total confusion.

The desktop would not work and I could not access the printer.

Did a release renewal on the Desktop and noticed a strange thing. The DHCP server assigned it a new address, but did not have a name for it and it get only a 1 minute lease. When that times it and renewed the lease then it got the desktop name and gave it a 24 hr lease.

Anyway I restricted the router DHCP server to .2 to .31. That is probably 8 times the number that I will ever use at any one time.

And set the printer for static at .32

And set that address in the laptop printer port.

And the princesses kissed the frog and everyone lived happily ever after.