Here's a happy little conundrum for you

[Bugs]

Hiya,

 

We've recently moved all of our workstations and laptops from using DHCP to having static IP's and reducing the scope to about 30 or so spaces just for devices we have missed, so they are still able to connect to our systems.

 

recently we've started noticing machines which should have a static IP are reporting IP conflicts, its difficult to trace the other device which has the same IP so we end up switching it to DHCP to solve it, obviously we cant do this for many machines or we will run out of address's

 

I was interested to know if anyone else had reported this. we have a 2000 server and XP clients.

[localzuk]

The way we are dealing with running out of IP addresses is to use a larger range! Why can't you do this?

[AIT]

Hiya,

 

We've recently moved all of our workstations and laptops from using DHCP to having static IP's and reducing the scope to about 30 or so spaces just for devices we have missed, so they are still able to connect to our systems.

 

recently we've started noticing machines which should have a static IP are reporting IP conflicts, its difficult to trace the other device which has the same IP so we end up switching it to DHCP to solve it, obviously we cant do this for many machines or we will run out of address's

 

I was interested to know if anyone else had reported this. we have a 2000 server and XP clients.

 

why dont you do a network scan to identify all the ip's in use?

[Gatt]

Another solution

 

Shove them all back on DHCP

Get a list of MAC addresses for the PCs

Reserve an IP for each MAC address

That way PC's are still technically on DHCP (recommended) but will always get the same IP Address

 

This also eliminates the chance of duplicate IPs as the Reserved IPs are flagged as being leased and thereby not available..

[Bugs]

we cant use a larger range because we want all machine to have static IP's and if we increase the range we will get alot more conflicts.

 

iv done network scans but thats not really solving why it happens tells me where the address's are in use and thats it.

[plexer]

we cant use a larger range because we want all machine to have static IP's and if we increase the range we will get alot more conflicts.

 

iv done network scans but thats not really solving why it happens tells me where the address's are in use and thats it.

 

You like making work for yourself then?

 

Ben

[AIT]

your dhcp scope isnt overlapping your static adresses is it??

[tmcd35]

I'll ask the obvious two questions, are you 100% sure the scope is set up correctly on the server and it is set to only assign IP from you 30 address range? And, are you 100% sure there are no other DHCP servers lurking on the network? Checked none of the Wireless Access Points have DHCP turned on by accident, for example.

[sparkeh]

we want all machine to have static IP's

 

Just interested why you want this?

Its not really recommended to do this on the actual client and creates a lot more work for you as you appear to be finding. If you really want static addresses then how about the suggestion above to use reservations in DHCP using MAC addresses, that way you won't get conflicts.

Edited December 11, 2009 by sparkeh
Can't flippin' spell today

[localzuk]

we cant use a larger range because we want all machine to have static IP's and if we increase the range we will get alot more conflicts.

 

Why do you? And no it doesn't. Static allocation is best done via DHCP - ie. you map MAC addresses to IPs at the DHCP server via reservations. The machines then have static addresses, and you don't have to do any physical configuration on the clients.

 

iv done network scans but thats not really solving why it happens tells me where the address's are in use and thats it.

 

If you have a machine which says there's a conflict, you disconnect it from the network - run a network scan and find out the name of the machine with the same IP. You can only get conflicts in a couple of ways - 1. you have given the same static address to 2 machines, 2. you have your DHCP scope overlapping your static address ranges and 3. there is a rogue DHCP server.

[Bugs]

I am 100% certain that the scope is setup correctly and the range we have is correct, That was my next port of call checking AP's.

[Edu-IT]

Why do you? And no it doesn't. Static allocation is best done via DHCP - ie. you map MAC addresses to IPs at the DHCP server via reservations. The machines then have static addresses, and you don't have to do any physical configuration on the clients.

That's the way I've done it when I need to.

[GrumbleDook]

Yep, DHCP reservations is the way to go and if you get an IP conflict you use the following process to eliminate the issue.

 

1 - You have laptop A which has a DHCP reservation, giving you an IP of x.x.x.5 ... this is based on the MAC address of that device.

2 - That device gets an IP conflict with another device somewhere but the person reporting it has closed the message box so you can't get the MAC address of the other machine.

3 - To keep things working you temporarily give Laptop A a new IP by changing the reservation within DHCP to something you are pretty sure will not clash.

4 - Have a look in the error logs on Laptop A to see if the MAC address of the other device is in there ... if not the run tools like The Dude on that address alone to identify the MAC address, the machine name and any other details you can.

5 - It is likely that the offending device has its IP assigned statically so you the best option you have is to add a reservation in ready, find the device and change it to DHCP so it gets the IP you want it to have.

6 - You can now change the reservation on Laptop back to what you originally wanted.

 

If you have everything on static addresses at the moment the best thing to do is to take this one set of devices at a time presuming you have tried to use contiguous addressing for each room.

 

The above is a tried and tested method and is a simplified version of a longer checklist I found on TechRepublic (which I couldn't find to link to ... which is why I wrote it out in the end).

[m25man]

I just plug in my etherscope, turn everything on drink tea check my emails post a couple on Edugeek then dump the report fix the problem and go home....

[HodgeHi]

You can also script the creation of DHCP scope and the reservations. How i did it was to audit the clients and take down the mac addresses (therefore getting rid of another tedious task in the process) and using this data, i created a database of the clients and their associated addresses with corresponding IPs to reserve, IIRC. This was then used with a command line util (can't recall which one but i will see if i can find out) to create the DHCP scope and it's reservation table.

 

You can also create the DNS table as well using the IPs and the hostnames IIRC. I'm sorry it's so vague it was over a year and a half ago.

 

But i will see if i can get more details if you want.

[Dos_Box]

I just plug in my etherscope, turn everything on drink tea check my emails post a couple on Edugeek then dump the report fix the problem and go home....

 

LOL. I misconstrued the 'dump' part of that post!

[john]

I just plug in my etherscope, turn everything on drink tea check my emails post a couple on Edugeek then dump the report fix the problem and go home....

Did you rob a bank to afford that? I'd love a Fluke Etherscope I miss my big range of Fluke Tools

[m25man]

Without doubt after the Leatherman it's the best tool I've ever owned and yes it cost me £6.5k how else did you expect me to have paid for it!

[apeo]

LOL. I misconstrued the 'dump' part of that post!

 

LOL.

 

Dont get why theres a need for static assignment... surely if you going back to old school static then you need to do everything the long way i.e. have a list of all devices statically assigned and then go through all the devices to make sure they are assigned the right ip. This assumes that the issue is with a misconfigured static ip, if the problem is a rogue DHCP then that shouldnt be to figure out.