DHCPNotes

DHCPNotes

---

DHCP Servers

If a client tries to renew an address already owned by some other computer on the network, the DHCP server responds with a DHCPNAK packet that basically tells the client, "You can't have that address; give it up."

You can force a client to release its IP address before its lease expires by using the ipconfig /release command. You can force a client to attempt to renew a lease with ipconfig /renew . You might use this procedure when you physically move a computer from one subnet to another in your internetwork.

The DHCP lease and renewal process occurs separately for each network adapter that is configured for automatic TCP/IP addressing. Each adapter in a multihomed computer must have its own unique IP address to communicate using TCP/IP.

If a DHCP server has a network adapter with more than one IP address configured on it, only the first address is used to service DHCP clients .

If you want to reserve an IP address for a client but there is more than one DHCP server available to the client, you must configure the same reservation on each DHCP server.

The DHCP Server service is relatively disk- intensive , so take this into account when selecting the hardware for your server. RAID may be an option for DHCP servers that service a large number of clients.

If the configuration of your network rarely changes, you can increase the duration of DHCP leases or make it unlimited. If you frequently move computers around or have a lot of mobile computers, you can reduce the lease duration. Also, if you have a lot of extra, unassigned IP addresses, you can increase the duration of DHCP leases or make it unlimited. If you have barely enough addresses, reduce the lease duration. Note that dial-up clients should have leases of short duration, typically three days or less.

The DHCP Users group provides read-only access to the DHCP console. It can't modify the DHCP server settings. To give a user the ability to modify DHCP server settings, add the user to the DHCP Administrators group.

If your DHCP server stops unexpectedly, check the System log in Event Viewer. If this doesn't help, check the DHCP server audit log.

DHCP Relay Agents

WS2003 computers can be configured to operate as DHCP relay agents in two different ways:

• As a server on the subnet (for example, a file/print server) that also functions in the role of a DHCP relay agent

• As an IP router connecting two or more subnets (the computer must be multihomed) that also functions on one or more network interfaces as a DHCP relay agent

Many third-party routers can also be configured as DHCP relay agents. You typically configure the agent by specifying the IP Helper Address of the DHCP server to which the agent forwards DHCP client traffic.

To view DHCP relay-agent statistics, select the DHCP Relay Agent node in the console tree and read the details pane.

See Also

DNS , netsh , TCP/IP