Chapter 9
| General Security Measures
DHCPv4 Snooping
– 315 –
will be performed on any untrusted ports within the VLAN as specified by the ip
dhcp snooping trust command.
◆ When the DHCP snooping is globally disabled, DHCP snooping can still be
configured for specific VLANs, but the changes will not take effect until DHCP
snooping is globally re-enabled.
◆ When DHCP snooping is globally enabled, and then disabled on a VLAN, all
dynamic bindings learned for this VLAN are removed from the binding table.
Example
This example enables DHCP snooping for VLAN 1.
Console(config)#ip dhcp snooping vlan 1
Console(config)#
Related Commands
ip dhcp snooping (306)
ip dhcp snooping trust (317)
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 | {tr101 {node-identifier {ip | sysname} |
no-vlan-field}
no dhcp snooping information option circuit-id [tr101 no-vlan-field]
string - An arbitrary string inserted into the circuit identifier field.
(Range: 1-32 characters)
tr101 node-identifier - The remote ID generated by the switch is based on
TR-101 syntax (R-124, Access_Node_ID).
ip - Specifies the switch’s IP address as the node identifier.
sysname - Specifies the system name as the node identifier.
tr101 no-vlan-field - Do not add “:VLAN” in TR101 field for untagged
packets.
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