DHCP Problem, Please Help!

[James]

I have a 2000 Server on subnet 10.0.1.x, and I have a
superscope set up with scopes from 10.0.1.x - 10.0.6.x. I
have 6 networks in different cities on my WAN, and each is
assigned a different one of these subnets. My problem is
this, initially and client in any city gets their IP
address correctly, i.e. the guy in Chicago on the 10.0.2.x
subnet gets a 10.0.2.x ip address. But, say that guy is a
laptop user, and he travels to Kansas City, which is the
10.0.3.x subnet, no matter how many times you release amd
renew, or reboot or whatever, he still keeps getting a
10.0.2.x address. And this addy will not work on the
10.0.3.x subnet.

Any ideas would be greatly appreciated. I have already
tried deleting the ip lease out of the invalid subnet, but
the DHCP server keeps reassigning it.

 

[Shane Brasher]

Hello,

A superscope is a first come first serve type of DHCP offer. There is no
way to regulate which scope he will get an IP address from. The super scope
was meant to be used for clients on the same wire. If you delete the super
scope and have regular scopes to service your clients, you should be OK
assuming of course your routers/switches are performing the proper DHCP
relaying to the server.

A client boots up from the 10.0.3.x subnet and the router takes the request
and appends the giaddr field in the packet and sends it to the DHCP server.
The DHCP server takes the request and sees that it is a request from the
subnet of 10.0.3.x. It will then choose from that scope range an ip
address to lease out. It will send the request to the relay agent. A DHCP
server uses the giaddr field to determine the subnet that sent the request
for IP addresses and which IP addresses to offer. (If the giaddr field is
blank, the DHCP server assumes that the request is from the local subnet.)
The request should from that point go to the client to the proper subnet
with the proper IP.

With a superscope in place, all scopes appear to be acting as one scope. It
will be a gamble as to which IP address he will get.

Delete the superscope and he should be fine.


Shane Brasher
MCSE (2000,NT),MCSA, A+
Microsoft Platforms Support
Windows NT/2000 Networking

 

[James]

Thank you very much. I misread another article about
superscoping, and that is why I created the superscope in
the first place. I removed it last night and now all of my
clients are receiving addresses as they are supposed to.

James