3Com 4500 Configuration Manual page 402

Enable DHCP-snooping Option 82 support on the switch and set the remote ID field in Option 82 to
the system name of the switch. Set the circuit ID sub-option to abcd in DHCP packets from VLAN
1 on Ethernet 1/0/3.
Network diagram
Figure 3-6 Network diagram for DHCP-snooping Option 82 support configuration
Configuration procedure
# Enable DHCP snooping on the switch.
<Switch> system-view
[Switch] dhcp-snooping
# Specify Ethernet 1/0/5 as the trusted port.
[Switch] interface ethernet 1/0/5
[Switch-Ethernet1/0/5] dhcp-snooping trust
[Switch-Ethernet1/0/5] quit
# Enable DHCP-snooping Option 82 support.
[Switch] dhcp-snooping information enable
# Set the remote ID sub-option in Option 82 to the system name (sysname) of the DHCP snooping
device.
[Switch] dhcp-snooping information remote-id sysname
# Set the circuit ID sub-option in DHCP packets from VLAN 1 to abcd on Ethernet 1/0/3.
[Switch] interface ethernet 1/0/3
[Switch-Ethernet1/0/3] dhcp-snooping information vlan 1 circuit-id string abcd
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