Dell PowerConnect 5524P User Manual page 566

As shown in Table 21-1, the DHCP Snooping Binding database is updated by
interception of DHCPACK, DHCPDECLINE and DHCPRELEASE packets,
and is stored in non-volatile memory.
Even if a port is down, its entries are not deleted.
NOTE:
Only DHCP requests on untrusted ports are maintained in the Binding
database.
Limitations
The following limitations apply:
• Enabling DHCP snooping uses TCAM resources.
• The switch writes changes to the binding database only when the switch
system clock is synchronized with SNTP.
• The switch does not update the Binding database when a station moves to
another interface.
Global Parameters
Use the Global Parameters page to:
• Enable/disable DHCP snooping globally.
• Determine whether to forward or filter DHCP packets received from
untrusted interfaces, whose source MAC address and the DHCP client
MAC address do not match.
• Determine whether to forward or filter DHCP packets, received from
untrusted interfaces, with option-82 information.
• Set Binding database update interval.
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Dell PowerConnect 55xx Systems User Guide