User Manual UMN:CLI
V5808
351
ip dhcp snooping database
renew auto retry <1-50>
Specifies the maximum number of retry attempts to
automatically restore the DHCP snooping DB file from
the TFTP server.
The file of DHCP snooping database entries is stored in a remote location accessible
through TFTP.
8.5.7.9 ARP Inspection Start Time
This function sets the time before ARP inspection starts to run. Before setting this, ARP
inspection should be turned on. ARP inspection checks validity of incoming ARP packets
by using DHCP snooping binding table and denies the ARP packets if they are not
identified in the table.
However, the V5808 may be rebooted with any reason, then DHCP snooping binding
table entries, which are dynamically learned from DHCP packets back and forth the
V5808, would be lost. Thus, ARP inspection should be delayed to start during some time
so that DHCP snooping table can build entries. If no time given, ARP inspection sees
empty snooping table and drop every ARP packet.
To specify the ARP inspection delay time, use the following command.
ip dhcp snooping arp-inspection
start <1-2147483637>
Configures the ARP inspection delay time. If reboot,
ARP inspection resumes after the time you configure.
1-2147483637: delay time (unit: second)
no ip dhcp snooping arp-
inspection start
Delete the configured ARP inspection delay time.
8.5.7.10 DHCP Snooping with Option82
In case of L2 environment, when forwarding DHCP messages to a DHCP server, a DHCP
switch can insert or remove DHCP option82 data on the DHCP messages from the clients.
In case of a switch is enabled with DHCP snooping, it floods DHCP packets with DHCP
option82 field when the DHCP option82 is enabled. This allows an enhanced security and
efficient IP assignment in the Layer 2 environment with a DHCP option82 field.
If DHCP snooping is enabled in the system of V5808, DHCP packets includes DHCP
option82 field by default.
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