Windows 7: IP changing

Hello

I have a problem with a network so if you could help I will be grateful.

I have a network witch has the IP 20.1.1.x, 20.1.2.x, 20.1.3.x. For a few day some of the computers receive another IP (192.168.1.x). We are using here swithches, routers...

Could you tell me what is the problem?



(Sorry for my english)

Well I can see only 2 ways this would happen. Either your DHCP server is handing out ip addresses in the 192.. range (check in the router settings) or the computers are obtaining ip from another device other than the intended device. Unless the no. of computers is very large, you can also try assigning ip addresses manually in the 20.. range.

Until 2 weeks ago everything worked just fine.
I already assigned the IP manually on the computers that have that problem, but this is only a temporary solution, because the number of the computer is large and it's not an option.

Somebody told me that maybe the output of a router could be connected to the output of another router. Could this be the problem?

If you have multiple routers you need to make sure only one is assigning ip addresses, so switch off dhcp serve on the other. If the second router is connected via CAT5 cable, it must be a lan port to lan port connection with the mother router. Basically the second router should just act as a device for the mother router.

A switch could cause a problem like that? Or only a router?
Because I have here many swithches (3COM, Cisco, Trendnet; 8 ports, 24 ports, 48 ports).

If it's a home (or small business for that matter) network, check this out: Multi Router Network - Configure It may point you to where you've gone wrong.

Generally speaking it's best to only have one DCHP server on a network, unless you have a bit system and you don't have enough IP's to go around. I agree with Bills assesment, that another router is handing out IP's when it shouldn't be.

A switch doesnt require any ip address or dhcp configuration so it does greatly simplify things.

So are there different subnetworks here or just one large network? And wired/wireless/hybrid?

I didn't create and configure the network. It was already created when I get here and it's pretty big. There are also here 6 Access points (these are working as routers, right?).

Than you guys. I will read that tutorial.

There is one big network witch has access to Internet. Most of computers use the wired connection, and the wirelles is used only by a few laptops, sometimes. There are 6 access points for wireless coverage.

Actually, what would make this process much quicker, rather than trying to figure out which router is to blame manually, is this.

From a machine that has the "wrong" ip address (ie 192.*) open command prompt and type ipconfig /all and post back the results.

If you could do the same to one that is on the "right" network as well that would make things much easier....