Problems might occur if the clients cannot receive an IP address
or the configuration information. An IP address is leased to a client through
a four-step process between the client and the DHCP server.
All four steps must take place before the client receives an IP address.
Refer to DHCP client-server interaction for details about the four-step process.
Here are some common reasons for this problem.
- The client is connected to a subnet that is not configured in the DHCP
server.
- Check the DHCP configuration and verify that all subnets managed by the
DHCP server are listed in the configuration. If you are unsure about which
subnets should be managed by the DHCP server, refer to Network topology considerations.
- The DHCP DISCOVER message from the client cannot reach the DHCP server.
- If the DHCP server does not have an IP address on the client's subnet,
there must be a router or DHCP/BOOTP relay agent that can forward the client's
DHCP DISCOVER message to the DHCP server. For more information, refer to Relay
agents and routers. In addition to receiving the broadcast message, the server
needs to be able to send reply packets back to the client's subnet.
- If your iSeries™ server
is multihomed, you might need to add a Subnet Group to the DHCP
configuration. For more detail on configuring DHCP for a multihomed server,
see Example: DHCP and multihoming. This example describes what needs to be
done to the DHCP configuration so that the client's broadcast message is received
by the server.
- The DHCP server does not have any available addresses for the client in
the address pool.
- You can use the DHCP Server Monitor to see which addresses are currently
being used by the DHCP server. Managing leased IP addresses provides more
details about using the DHCP Server Monitor. If the DHCP server has run out
of available addresses, you might need to add more IP addresses to the address
pool, shorten the lease time, or delete permanent leases that are no longer
required.