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3. Troubleshooting Functional Failures in Operation
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Figure 3-9: DHCP Server Failure Analysis Procedure
(a) Checking configuration
IP addresses may not be assigned to clients due to configuration setting errors for resources on the DHCP server. The
followings are the steps to check the configuration:
1. Confirm that the configuration has the "ip dhcp pool" setting including the network setup of the IP address to be
assigned to DHCP clients.
2. Using configuration command ip dhcp excluded-address, confirm that the number of pooled IP addresses
in the configuration to be assigned to the DHCP clients is not fewer than the number of clients to be used
concurrently.
3. If communication between a client and another system is disabled after an address is assigned by this system to the
client, the default router may not have been set. Execute configuration command default-router to confirm
that the router address (default router) of the network to which the client is connected has been set up (see the manual
"Configuration Commands").
4. Check the setting of the system as the DHCP relay agent. If this system is also used as the relay agent, see "(1)DHCP/
BOOTP relay communication failure."
(b) Checking the log message and interface
On possible cause for the server not assigning IP addresses to clients, the communication client between cliant and
server may have been disabled. Check the log message displayed on this system or the interface up/down status using
the show ip interface command. For the procedure, see "3.6.1 Communication Is Disabled or Is Disconnected."
(c) Identifying the extent of the failure (performed from this system)
If no failure is found on this system, a failure may exist somewhere in the route between this system and the remote
system. The procedure to locate the failure in the route to the remote system and identify the failure range is as follows:
1. Log in to the system.
2. If a router is provided between the server and the client, use the ping command to verify communication of the
system (router) between the server and the other system (DHCP client) to which communication is disabled. If
<IP addresses cannot be assigned to clients.>
Check the configuration.
Verify the failure occurrence using the show logging
command and the show ip interface command.
No failure on this system
(Connected via relay
agent)
No failure on this
system
(Connected directly)(
Verify the setting information of filter
and QoS.
Refer to
"(1)DHCP/BOOTP relay communication failure."
A failure occurred on
this system
see the manuals "Message Log
Reference" and "3.6.1 Communication Is
Disabled or Is Disconnected" and
perform the actions described in [Action]
associated with each log message.