Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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2. The network configuration is changed.
3. The DHCP server fails.
First, check for cause 1. Described below are likely examples of incorrect configuration. For cause
2, check the differences in the network configuration before and after the change to uncover any
cause that could disable communication. You might have checked the client and server settings
(such as network card settings and cable connections) and concluded that cause 3 applies. For
example, the configuration and network configuration are correct, but IP communication is not
possible due to disabled allocation of IP addresses to clients. In such a case, see (b)Checking the
log messages and interface through (e)Checking the filters and QoS configuration information for
details.
Use the following flowchart to isolate the fault location to identify the cause of the problem.
Figure 3-8: Failure analysis procedure on the DHCP server
(a) Checking the configuration
It can be assumed that IP addresses cannot be assigned to clients because the resources on the
DHCP server are configured incorrectly. To check the configuration, do the following:
1. In the configuration, make sure there is an
ip dhcp pool setting that contains the network
setting for the DHCP addresses to be assigned to the DHCP clients.
2. In the configuration, make sure the number of IP address pools to be assigned to a DHCP
client is larger than the number of concurrently used clients set in the
ip dhcp
excluded-address configuration command.
3. If the Switch has assigned addresses to the clients but the clients cannot communicate with
other devices, the default router might have not been set. Make sure that the router address
(default router) of the network to which the clients are connected has been set by the
default-router configuration command (see the manual Configuration Command
Reference).