CLI Reference Guide-R04

Chapter 9 | General Security Measures
DHCPv4 Snooping
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sub-type - Distinguishes different types of circuit IDs.
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sub-length - Length of the circuit ID type
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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,
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eth - The second field is the fixed string “eth”
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slot - The slot represents the stack unit for this system.
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port - The port which received the DHCP request. If the packet arrives over
a trunk, the value is the ifIndex of the trunk.
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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.
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The ip dhcp snooping information option circuit-id command can be
used to modify the default settings described above.
◆ The format for TR101 option 82 is: “<IP> eth <SID>/<PORT>[:<VLAN>]”. Note
that the SID (Switch ID) is always 0. By default the PVID is added to the end of
the TR101 field for untagged packets. For tagged packets, the VLAN ID is always
added.
EXAMPLE
This example enables the use of sub-type and sub-length fields for the
circuit-ID (CID) and remote-ID (RID).
Console(config)#no ip dhcp snooping information option encode no-subtype
Console(config)#
ip dhcp snooping
information option
remote-id
This command sets the remote ID to the switch’s IP address, MAC address, or
arbitrary string, TR-101 compliant node identifier, or removes VLAN ID from the end
of the TR101 field. Use the no form to restore the default setting.
Syntax
ip dhcp snooping information option remote-id
{ip-address [encode {ascii | hex}] |
mac-address [encode {ascii | hex}] | string string [sub-option port-
description[delimiter string]] |
tr101 {node-identifier {ip | sysname} | no-vlan-field}
no ip dhcp snooping information option remote-id
[ip-address encode] |
[mac-address encode] |
[tr101 no-vlan-field]
[string sub-option port-description delimiter]