Linux Format forums

Re: Static IP and DHCP ranges

wyliecoyoteuk — Mon Aug 13, 2012 8:56 pm

Author: wyliecoyoteuk

Posted: Mon Aug 13, 2012 8:56 pm

DNS-SD is DNS service discovery, part of Zeroconf.
Another way of automating device management.
Not all network printers support it, but more and more will I expect.

Re: Static IP and DHCP ranges

guy — Mon Aug 13, 2012 7:53 pm

Author: guy

Posted: Mon Aug 13, 2012 7:53 pm

On subnet masks:

Each of those 123 triplets represents a binary byte. Four triplets = 64 bits. That is how long every IPv4 address is.

The subnet mask defines your "subnet" - those bits of the IP address that must be constant for every device on your network. For a "Class C" subnet it is 11111111.11111111.11111111.00000000 - 24 1's followed by 8 0's.

This means that for devices to be on the same network, those first 24 bits of their addresses must all be the same, and the last 8 must be unique to each device.

This is the default mask for most routers, including yours. It means that the third "triplet", whether a 1 or a 2 or anything else (i.e. 001 or 002 but we don't bother to write leading zeroes), must be the same for all hosts.

Yes, you can change the mask to 255.255.0.0 (I think that makes it a "Class B" network), and big companies have to do that sort of thing. But it's probably easier and less confusing to do it the default way.

On printers and IP addressing

My network printer installed itself on the network automatically, I simply plugged in and switched on. In fact, it must reconnect every time it is switched on. My Linux box happily found it in several guises, one via its IP address, another via dnssd://[something.like.a.domain.name]/ which suggests to me that it is under the thumb of my router, which acts as a dhcp service and therefore manages my network settings for me, using dynamic IP addressing.

If I looked on successive days, I'd probably see different IP addresses. So I just installed the printer as dnssd://[something.like.a.domain.name]/ and I've not had a printer access problem since.

Static IP allocation? Why make a yoke for your own neck?

Re: Static IP and DHCP ranges

wyliecoyoteuk — Mon Aug 13, 2012 9:42 am

Author: wyliecoyoteuk

Posted: Mon Aug 13, 2012 9:42 am

I regularly set up MFDs (Multi Function Devices, used to be called photocopiers) on networks, and wherever possible, I try to persuade the sysadmin to use DHCP.
Why?
DHCP can be used for more than just an IP address.
A properly configured DHCP server can also issue DNS servers and other useful info.If you change the IP range, gateway or DNS server, DHCP can automatically update it on all clients. All you need to know is the MAC address.

MFDs are not just printers, they are also document servers, email servers (and clients) and log on to servers to save scanned files in folders via SMB, FTP or NFS, so if you have several of them on a network (we have some customers with 40 or 50), fixed IPs become a pain. They can also use DNS to resolve host names for target servers, and LDAP searches for email addresses, thus avoiding even more manual input.

However, for a home user, it is not advisable to just use DHCP without reserving the address, as often happens.

Re: Static IP and DHCP ranges

nelz — Mon Aug 13, 2012 8:43 am

Author: nelz

Posted: Mon Aug 13, 2012 8:43 am

Nuke wrote:

Not necessarily. My new network printer has a constant address supplied by DHCP. I could have assigned a static address, but that would have meant reading the manual and working with a 2 line display and fiddly buttons to set it.

One big advantage of setting all your "static" addresses by DHCP is that the configuration is set in one place, not spread all over the network, making administration much easier.

Re: Static IP and DHCP ranges

dandnsmith — Mon Aug 13, 2012 7:23 am

Author: dandnsmith

Posted: Mon Aug 13, 2012 7:23 am

Quote:

That being the case, I'd rather nail down my printer with a fixed IP address. To me, the only point of DHCP is for portable devices. What have I missed? Question

I'd normally agree, but just recently I had occasion to set up a printer/server for testing in one environment, but final use in another where I didn't know what the address ranges were being used. Here I found using DHCP to be easier, as it happened to be easier to carry the MAC for the printer rather than reconfigure the printer.

Re: Static IP and DHCP ranges

Nuke — Sun Aug 12, 2012 11:24 pm

Author: Nuke

Posted: Sun Aug 12, 2012 11:24 pm

scarydeath wrote:

wyliecoyoteuk wrote:

On another note, it is a really bad idea to use DHCP for printers.

I assume you mean because the computer accessing the printer will need to be told where it is - i.e. the IP address changes on each request?

I have set up a small printer server with DHCP. I instruct the router to reserve a specific IP address for this device, and therefore all the benefits of DHCP (easy set up) are retained, whilst a "static" IP address is used.

Why is DHCP easier to set up for a printer? I told my print server to use a certain static address, then told my PCs to use that address for their printer. If you set up a reserved DHCP address instead as you do, doesn't that amount to the same work?

That being the case, I'd rather nail down my printer with a fixed IP address. To me, the only point of DHCP is for portable devices. What have I missed?

Re: Static IP and DHCP ranges

wyliecoyoteuk — Sun Aug 12, 2012 8:47 am

Author: wyliecoyoteuk

Posted: Sun Aug 12, 2012 8:47 am

scarydeath wrote:

wyliecoyoteuk wrote:

On another note, it is a really bad idea to use DHCP for printers.

Why?

I assume you mean because the computer accessing the printer will need to be told where it is - i.e. the IP address changes on each request?

I have set up a small printer server with DHCP. I instruct the router to reserve a specific IP address for this device, and therefore all the benefits of DHCP (easy set up) are retained, whilst a "static" IP address is used.

That's fine. In fact I do that too for all in ones that need DNS etc.
But DHCP without reservation is definitely not a good idea, as if the router or the printer are turned off for longer than the printerDHCP lease period, it will get a different address.

Re: Static IP and DHCP ranges

scarydeath — Sat Aug 11, 2012 10:10 pm

Author: scarydeath

Posted: Sat Aug 11, 2012 10:10 pm

wyliecoyoteuk wrote:

On another note, it is a really bad idea to use DHCP for printers.

Re: Static IP and DHCP ranges

pk_fox — Sun Jul 08, 2012 1:48 pm

Author: pk_fox

Posted: Sun Jul 08, 2012 1:48 pm

purplepenguin wrote:

Hello

I have several machines on my LAN. I like to assign static IP addresses to the ones that are permanent such as HTPCs, Main PC, Media Server. and leave the others such as phones, Wii, Netbooks and Printer to DHCP.

I wanted to use different IP ranges for different classes of machines eg.
Devices assigned DHCP on say 192.168.1.1 -192.168.1.50
Clients such as Main PC, HTPC and Kids PC on 192.168.1.51 -
and all infrastructure servers, printers etc on 192.168.2.1 -

For some reason I cannot use the 192.168.1.x range I can only use the 192.168.2.x range.

I think this may be due to my routers setup in particular the subnet mask? But I'm not sure and I'm getting confused and knotted up from google results.

Here are the router details
My routers address is 192.168.2.1
My DHCP pool range is 192.168.2.2 - 192.168.2.50
Subnet mask is 255.255.255.0

The DHCP range has the first 3 blocks greyed out so I cannot change the 2 to 1.

If I change the subnet mask to 255.255.0.0 will I then be able to use the 192.168.1.x range

Many thanks

If you want to use the 192.168.1.x range just change your routers ip address to 192.168.1.1 and LEAVE THE SUBNET MASK ALONE !

Lee

Re: Static IP and DHCP ranges

towy71 — Sat Jul 07, 2012 8:42 pm

Author: towy71

Posted: Sat Jul 07, 2012 8:42 pm

I downloaded the pdf manual for your router and on page 39 it states:

Quote:

1.
IP Address
The �IP address� is the internal IP address of the Router. The
default IP address is �192.168.2.1�. To access the advanced setup
interface, type this IP address into the address bar of your browser.
This address can be changed if needed. To change the IP address,
type in the new IP address and click �Apply Changes�. The IP
address you choose should be a non-routable IP. Examples of a
non-routable IP are:
192.168.x.x (where x is anything between 0 and 255)
10.x.x.x (where x is anything between 0 and 255)
2.
Subnet Mask
There is no need to change the subnet mask. This is a unique,
advanced feature of your Belkin Router. It is possible to change
the subnet mask if necessary; however, do NOT make changes to
the subnet mask unless you have a specific reason to do so. The
default setting is �255.255.255.0�.

I have a Belkin router and can change the IP if I want

Re: Static IP and DHCP ranges

purplepenguin — Sat Jul 07, 2012 7:43 pm

Author: purplepenguin

Posted: Sat Jul 07, 2012 7:43 pm

wyliecoyoteuk wrote:

Yes, that's right, but really unnecessary.
255.255.255.0 gives you access to 254 addresses, more than you can really expect to use for a home network.
Changing it to 255.255.0.0 would give you access to over 64 thousand addresses.
I would set the DHCP range to the first 49 addresses, 192.168.2.2-192.168.2.50
Then allow fixed addresses in the rest of the 50-254 range
e.g. servers 126-192, hardware 193-254
There are good arguments for limiting the number of available addresses, and none really for increasing them..
I know of some installations where the mask is set to 255.255.255.248, for example, to prevent casual connections.

On another note, it is a really bad idea to use DHCP for printers.

Anyway IPv6 will change all of this forever.

Cool thanks, I know I wont need more than the 254 addresses and I'm happy with my IP scheme I was just curious as to why I couldn't use the 192.168.1.x and started to look at subnets on google.

I used to use static IP's for my printer (Epson sx515w) but when it broke I bought a sx435w which to the best of my knowledge can only use DHCP and yes I do have problems from time to time when the IP address changes, that's why I never turn it off any more.

lee

Re: Static IP and DHCP ranges

wyliecoyoteuk — Sat Jul 07, 2012 7:16 pm

Author: wyliecoyoteuk

Posted: Sat Jul 07, 2012 7:16 pm

Yes, that's right, but really unnecessary.
255.255.255.0 gives you access to 254 addresses, more than you can really expect to use for a home network.
Changing it to 255.255.0.0 would give you access to over 64 thousand addresses.
I would set the DHCP range to the first 49 addresses, 192.168.2.2-192.168.2.50
Then allow fixed addresses in the rest of the 50-254 range
e.g. servers 126-192, hardware 193-254
There are good arguments for limiting the number of available addresses, and none really for increasing them..
I know of some installations where the mask is set to 255.255.255.248, for example, to prevent casual connections.

On another note, it is a really bad idea to use DHCP for printers.

Anyway IPv6 will change all of this forever.

Re: Static IP and DHCP ranges

purplepenguin — Sat Jul 07, 2012 6:16 pm

Author: purplepenguin

Posted: Sat Jul 07, 2012 6:16 pm

towy71 wrote:

What make and model router?

Belkin F5D8233 4-v3

On the LAN setting page I can change the routers IP address and the Subnet Mask except for the first 255 of the subnet which is greyed out.

As far as I understand subnet masks ( I'm probably wrong) the 255's refer to the network and the 0's refer to the hosts. So a subnet of 255.255.255.0 as mine is set now means the last part of the IP is the host 192.168.2.x. If I change the subnet mask to 255.255.0.0 wouldn't that mean I could use IP addresses 192.168.x.x.

Thanks
Lee

Re: Static IP and DHCP ranges

towy71 — Sat Jul 07, 2012 5:06 pm

Author: towy71

Posted: Sat Jul 07, 2012 5:06 pm

What make and model router?

Re: Static IP and DHCP ranges

purplepenguin — Sat Jul 07, 2012 4:21 pm

Author: purplepenguin

Posted: Sat Jul 07, 2012 4:21 pm

Dutch_Master wrote:

The router came pre-configured for a private range Class C network. You're advised to assign static addresses either at the beginning or end of the range. Or set up a bridge that connect both subnets.

Thanks Dutch Master. I keep the DHCP pool to 192.168.2.2 -192.168.2.50
I assign all client pcs to the range 192.168.2.111 - 192.168.2.199 and
Servers to 1912.168.2.200 -192.168.2.255
I know this gives me more than enough addresses for a simple home lan I'll never use up all the available addresses.

I was just wondering if it would be as simple as changing the subnet mask on the router from 255.255.255.0 to 255.255.0.0 and restarting the router. To allow me to use the 192.168.1.x range.I know I would have to edit the network connections on all machines to reflect the subnet change.