Novell NETWARE 6-DOCUMENTATION Manual page 1711

Cause—An unauthorized DHCP server has been configured by someone
attempting to control or disrupt your network. The unauthorized DHCP
server is assigning IP addresses and other configuration parameters that
have already been assigned to other nodes by an authorized DHCP server.
The result is that nodes are assigned duplicate IP addresses or incorrect
configuration parameters. Incorrect configuration parameters can
interfere with a node's ability to communicate to the network in any
number of ways. Incorrect parameters can even be used to cause a node
to connect to a server that is controlled by an unauthorized user, thereby
allowing the unauthorized user to take control of the client.
Solution—Find the unauthorized DHCP server and disable it or
disconnect it from the network.
Problem—A Windows 95 client cannot acquire a lease and responds with
the message Unable to obtain an IP network address
Cause—The Windows 95 DHCP client has a two-second timeout for the
time between when it accepts an offer of an IP address in a message sent
to the server and the time it expects an acknowledgment of that
acceptance in a reply from the server. Other clients, such as Windows
NT*, have a four-second timeout.
Solution—Obtain the DCHCPUPD.EXE patch from Microsoft that
changes the timeout on Windows 95 clients from two seconds to four
seconds. The patch is dated 2/12/96 and includes a file named
VDHCP.386.
Problem—The use of mobile clients causes fewer leases to be available.
Cause 1—The mobile clients' lease is not released when the mobile client
moves to a remote office. This can occur when the remote office is on a
subnet different from that of the local office and the remote subnet is
serviced by a different DHCP server.
Solution 1— Determine the lease time assigned to this client. If the lease
is not released quickly enough, reduce the lease time. Otherwise, have the
client manually release the old IP address before it leaves the local office.
Cause 2—The mobile client uses two leases at the same time because it
cannot use the same lease and the same IP address at the new location.
Solution 2—Use one of the following solutions:
If the remote office is on a subnet different from that of the local
office and the subnet is serviced by the same DHCP server, verify
that the IPAssignmentPolicy attribute of the DHCP server object in
Troubleshooting 137