Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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No. Items to check and commands Action
2 Check the connection between the
DHCP server and the DHCP client
terminal.
Make sure the DHCP server is connected to a trusted port. If the
DHCP server is connected to an untrusted port, connect it to a
trusted port.
Make sure the DHCP client terminal is connected to an untrusted
port. If the DHCP client terminal is connected to a trusted port,
connect it to an untrusted port.
If the connection is correct, go to No. 3.
3 Try to clear the IP address on the
DHCP client terminal.
The Switch might have been restarted by, for example, turning the
power off and on. Clear the IP address.
Example: In Windows, in the Command Prompt window, execute
ipconfig /release and then ipconfig /renew.
4 Make sure the filtering and Layer 2
authentication functionality are
configured correctly.
Authentication might have failed because certain packets have
been discarded by filtering or Layer 2 authentication functionality
is used for the port or VLAN to which the terminal is connected.
Make sure the setting conditions for filtering and the Layer 2
authentication functionality in the configuration are correct.
(2) When the binding database cannot be saved
If the binding database cannot be saved when the DHCP snooping functionality is used,
take action according to the tables below.
(a) The database cannot be saved to internal flash memory
Table 3-19 When the save location for the binding database is internal flash memory
No. Items to check and commands Action
1 Use the show ip dhcp
snooping binding operation
command to check the time that
the database was saved.
If a hyphen (-) is displayed for Agent URL, go to No. 2.
Saving data might not have started yet because the wait-to-write
time
#
defined in the configuration has not elapsed since the save
event
#
. Wait a while.
If the wait-to-write time
#
since the save event
#
has elapsed and the
value displayed for Last succeeded time is either a hyphen (-) or
a time earlier than the time that the save event occurred, go to No. 3.
2 Use the show
running-config operation
command to check the
configuration.
If ip dhcp snooping database url flash is set, go to No. 3.
If ip dhcp snooping database url flash is not set, set the ip
dhcp snooping database url flash configuration command.