Publication date: Jan., 2009 47
Revision A1
Parameter description:
Trust Port 1：If DHCP snooping is enabled globally, and also enabled on the
VLAN where the DHCP packet is received, all DHCP packets
are forwarded for a trusted por. It set a trust port 1. available
port from 1 to 10. Default is disable
Trust port 2 : It set a trust port 2. available port from 1 to 10. Default is
disabled.
Option 82：It set the DHCP Option 82 function on the switch, Default is
disabled.
Action：It set the switch when received a client DHCP request packet then
action for filtering. available action : keep/ drop / replace.
Trust VID： It set a trust VLAN ID. available VID from 1 to 4094.
Server IP： It set a trust DHCP Server IP address for DHCP Snooping.
Note
：
Filtering rules are implemented as follows:
- If the DHCP snooping is disabled, all DHCP packets are forwarded.
- If DHCP snooping is enabled and also enabled on the VLAN where
the DHCP packet is received, all DHCP packets are forwarded for a
trusted port.
- If DHCP snooping is enabled and also enabled on the VLAN where
the DHCP packet is received, but the port is not trusted, it is
processed as follows:
* If the DHCP packet is a reply packet from a DHCP server, the packet
is dropped.
* If the DHCP packet is from a client, such as a DISCOVER, REQUEST
INFORM, DECLINE or RELEASE message, the packet is forwarded if
MAC address verification is disabled. However, if MAC address
verification is enabled, then the packet will only be forwarded if the
client’s hardware address stored in the DHCP packet is the same as
the source MAC address in the Ethernet header.
* If the DHCP packet is not a recognizable type, it is dropped.
- If a DHCP packet from a client passes the filtering criteria above, it
will only be forwarded to trusted ports in the same VLAN.
If a DHCP packet is from server is received on a trusted port, it will be
forwarded to both trusted and un-trusted ports in the same
VLAN.
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