Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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3.27.2 Problems related to saving the binding database
If binding information cannot be inherited at a device restart, probable causes are problems related
to saving the binding database. Isolate the cause of the problem according to the failure analysis
method described in the following table.
Table 3-85: Failure analysis method for problems related to saving the binding database
8 Make sure the DHCP server is connected to a
trusted port.
DHCP server response packets from an untrusted port are
discarded.
If the target DHCP server is an authorized one, set the
ip
dhcp snooping trust configuration command for the
port to which the DHCP server is connected.
Note that if the DHCP server on the Switch is used, the port
can be an untrusted port. If the DHCP relay on the Switch is
used, the DHCP server must be connected to a VLAN
exempt from DHCP snooping or to a trusted port.
9Use the
show ip dhcp snooping binding
command to check the binding information.
If the IP address cannot be updated after the device restarts,
check the save status of the binding database.
See 3.27.2 Problems related to saving the binding
database.
You might find that a different port or VLAN ID is
displayed in the binding information for a target entry (that
has the target MAC address and target IP address). In this
case, the connection port or the VLAN capacity limit might
have been changed after assignment of an IP address.
To continue using the current port or VLAN, obtain an IP
address again.
10 Other cases If any of the above actions do not resolve your problem,
check other functionality used in the device according to
this manual.
No. Items to check Action
1Use the
show mc or show flash command to
check whether there is a sufficient amount of
unused space in the flash memory or memory
card.
If there is not a sufficient amount of unused space, delete
unnecessary files to have an enough space.
If there is no problem, go to No. 2.
2 Check the storage destination of the binding
database.
If the binding database is saved in the flash memory, go to
No. 4.
If the binding database is saved in a memory card, go to No.
3.
3 Execute the
ls mc-dir command to check
whether the directory for saving the database
exists in the memory card.
If the directory does not exist, use the mkdir command to
create the directory.
If there is no problem, go to No. 4.
4 Check the setting of the
ip dhcp snooping
database write-delay configuration
command. Also, execute the
show ip dhcp
snooping binding command to check the last
time when the binding database was saved.
Even if the binding information is updated, the binding
database is not saved until the specified time passes. After
an IP address is distributed, wait a while until the specified
time passes, and then make sure that the last time when the
binding database was saved is updated.
If there is no problem, go to No. 5.
No. Items to check Action