Dhcp Snoopingtroubleshooting - Digitalchina Networks DCS-3950 series Manual

Command: logging source {default| m_shell|sys_event|anti_attack} channel
{ console | logbuff | loghost | monitor } [ level { critical | debugging | notifications |
warnings } [state { on | off } ] ]
Function： The details about this command are covered in the chapter on system log; the
data source of this command anti_attack records information about all kinds of
denfense to network attacks, including the automatic defense action log of dhcp
snooping.
Parameters：Please refer to System Logs chapter for detail.
Command mode：Global configuration mode
Default：Not covered
Usage Guide: Please refer to System Logs chapter for detail.
Example: Enable logging of network attacking in the system log buffer.
Switch(Config)#logging source anti_attack channel logbuff
19.3.1.3 show logging last FailureInfo
Command：show logging lastFailureInfo
Function：This command is used to display the system abnormal information recorded in
the flash. The defense action of DHCP Snooping is also recorded in the flash as system
abnormal information, and can be checked via this command.
Command mode：Admin Mode
Example: Display log information.
Switch# show logging lastFailureInfo

19.3.2 DHCP SnoopingTroubleshooting

If there are problems when using DHCP Snooping, please check the following
possible reasons:
Check whether the global DHCP Snooping switch is enabled;
If the port does not response to invalid DHCP Server packets, please check
whether the port has been set as an un-trusted port of dhcp snooping.
19.3.2.1 debug ip dhcp snooping packet
Command：debug ip dhcp snooping packet
no debug ip dhcp snooping packet
Function： This command is used to enable the DHCP SNOOPING debug switch to debug
the procedure of message processing.
Command mode：Admin Mode
Usage Guide: the information that DHCP SNOOPING is receiving messages from a
specific port.
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