npi Device ???

[Colin Butcher]

It sounds like a DHCP server address range overlap, which has ended up incorrectly updating some records in a dynamic DNS server.

It's worth ensuring that all the DHCP servers hand out unique non-overlapping address ranges with consistent DNS / gateway etc. information. It's also worth ensuring that your internal dynamic DNS servers (which may well be the same machines) are consistent across the internal network (along with your HOSTS files if they get used too).

I generally ensure that all non-client devices have fixed IP addresses - so that's your printers, network hardware, Windows servers, VMS servers, etc. You can either set those devices up manually, or arrange for your DHCP servers to statically tie specific MAC addresses to specific IP addresses, but still provide the information for the default gateway, DNS servers and so on. That latter method can make it easier to view the entire addressing scheme and to make changes that then get propagated to all DHCP clients when a machine boots or renews its DHCP lease.

For devices that don't need to talk to the 'net, or which don't need to refer to DNS names for devices other than themselves (printers, network equipment etc.), then it simplest to set them up manually. However, do remember to record the allocated addresses somewhere - and make sure they're not in the address range for DHCP assigned addresses.

A good general principle is to start the DHCP allocated addresses at the bottom of the address space and go up (eg: 10.51.42.1 to 10.51.42.149) and to start other devices at the top and come down (eg: 10.51.42.254 as the default gateway, 10.51.42.249 to 10.51.42.230 as network devices, 10.51.42.229 to 10.51.42.200 as printers, 10.51.42.199 to 10.51.42.150 as servers and other devices in need of static IP addresses).

Of course, most networks grow over time (or merge every so often) - which is why a structure to allocate names and addresses is the first thing you should design - and it should allow sufficient space and flexibility to expand without having to go back and change it.

Cheers, Colin (http://www.xdelta.co.uk).

[John Harper (Barbour)]

Many thanks for all your help.

DHCP was getting confused because a consultant installed a printer for testing with an address right in the middle of the DHCP range.

We install printers with fixed addresses of xxx.xxx.xxx.201 and upwards. The consultant assigned an address of xxx.xxx.xxx.113 which really confused things. We moved the printer so a "proper" address and everything seems fine.

If only he had asked first ...

[John Harper (Barbour)]

All fixed so once again, thanks.

John