ECS4660-28F_Management Guide-R03

C HAPTER 29 | General Security Measures
DHCPv4 Snooping
– 1122 –
ip dhcp snooping
information option
circuit-id
This command specifies DHCP Option 82 circuit-id suboption information. Use the
no form to use the default settings.
SYNTAX
ip dhcp snooping information option circuit-id string string
no dhcp snooping information option circuit-id
string - An arbitrary string inserted into the circuit identifier field.
(Range: 1-32 characters)
DEFAULT SETTING
VLAN-Unit-Port
COMMAND MODE
Interface Configuration (Ethernet, Port Channel)
COMMAND USAGE
◆ DHCP provides a relay mechanism for sending information about the
switch and its DHCP clients to the DHCP server. DHCP Option 82 allows
compatible DHCP servers to use the information when assigning IP
addresses, to set other services or policies for clients. For more
information of this process, refer to the Command Usage section under
the ip dhcp snooping information option command.
◆ Option 82 information generated by the switch is based on TR-101
syntax as shown below:
The circuit identifier used by this switch starts at sub-option1 and goes
to the end of the R-124 string. The R-124 string includes the following
information:
■
sub-type - Distinguishes different types of circuit IDs.
■
sub-length - Length of the circuit ID type
■
access node identifier - ASCII string. Default is the MAC address of
the switch’s CPU. This field is set by the ip dhcp snooping
information option command,
■
eth - The second field is the fixed string “eth”
■
slot - The slot represents the stack unit for this system.
■
port - The port which received the DHCP request. If the packet
arrives over a trunk, the value is the ifIndex of the trunk.
■
vlan - Tag of the VLAN which received the DHCP request.
Note that the sub-type and sub-length fields can be enabled or
disabled using the ip dhcp snooping information option command.
Table 119: Option 82 information
82 3-69 1 1-67 x1 x2 x3 x4 x5 x63
opt82 opt-len sub-opt1 string-len R-124 string