Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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2. Make sure that the key information and the authentication key specified on the DNS server
are consistent with the key information included in the DHCP server configuration (see the
manual Configuration Command Reference).
3. Make sure that the zone information specified on the DNS server is consistent with the zone
information included in the DHCP server configuration (see the manual Configuration
Command Reference). Also, make sure that both the normal and reverse lookups are set.
4. Make sure that DNS updating is set (see the manual Configuration Command Reference).
This setting is required to enable DNS updating because DNS updating is disabled by default.
5. Make sure that the domain name used by the client is consistent with the domain name
registered in the DNS server. If the DHCP is used to distribute domain names, make sure that
the setting is correct in the configuration (see the manuals Configuration Command Reference
and Operation Command Reference).
(b) Checking the time information
If an authentication key is used in DNS updating, in most cases, the difference between the UTC
time on the Switch and that on the DNS server must be five minutes or less. Use the
show clock
command to check the time information on the Switch, and if necessary, see the manual
Configuration Command Reference to synchronize the time information.
(c) Checking the log messages and interface
One of the causes of the failure in communication with the DNS server might be the
communication failure between the DNS server and the DHCP server. Check the log messages
displayed by the Switch or use the
show ip interface command to check whether the interface
status is
Up or Down. For details about the procedure, see 3.7.1 Communication is not possible or
is disconnected
(d) Identifying the range for a failure (from the Switch)
If a failure has not occurred on the Switch, a failure might have occurred somewhere on the route
between the Switch and the remote device. To identify the range for a failure in order to determine
the fault location on the route, do the following:
1. Log in to the Switch.
2. If there are devices such as a router between the DNS server and the DHCP server, use the
ping command to check the communication between the router and the remote device (DNS
server). If the communication with the remote device cannot be verified by using the
ping
command, execute the
ping command again to check communication with each of the devices
up to the client, beginning with the device closest to the Switch. For details about examples
of using the
ping command and how to interpret the execution result, see the Configuration
Guide.
3. If the DNS server and the DHCP server are directly connected, check the hub and cable
connections.
4. Select a suitable next step in the failure analysis flowchart depending on whether the range of
the failure determined by the
ping command is in the neighboring device or remote device.
(e) Checking the routing information
You need to check the routing information obtained by the Switch if (a) communication is still
disabled after address resolution with the neighboring device is completed, (b) communication is
disabled on the route to the remote device, or (c) the route to the remote device has a problem. To
carry out the check, do the following:
1. Log in to the Switch.
2. Use the
show ip route command to check the routing information obtained by the Switch.