Chapter 9
| General Security Measures
DHCPv4 Snooping
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DHCPv4 Snooping
DHCPv4 snooping allows a switch to protect a network from rogue DHCPv4 servers
or other devices which send port-related information to a DHCPv4 server. This
information can be useful in tracking an IP address back to a physical port. This
section describes commands used to configure DHCPv4 snooping.
Table 58: DHCP Snooping Commands
Command Function Mode
ip dhcp snooping Enables DHCP snooping globally GC
ip dhcp snooping information
option
Enables or disables the use of DHCP Option 82
information, and specifies frame format for the remote-id
GC
ip dhcp snooping information
option encode no-subtype
Disables use of sub-type and sub-length for the
CID/RID in Option 82 information
GC
ip dhcp snooping information
option remote-id
Sets the remote ID to the switch’s IP address, MAC
address, arbitrary string, or TR-101 compliant node
identifier
GC
ip dhcp snooping information
option tr101 board-id
Sets the board identifier used in Option 82 information
based on TR-101 syntax
GC
ip dhcp snooping information
policy
Sets the information option policy for DHCP client
packets that include Option 82 information
GC
ip dhcp snooping limit rate Sets the maximum number of DHCP packets that can be
trapped for DHCP snooping
GC
ip dhcp snooping verify
mac-address
Verifies the client’s hardware address stored in the DHCP
packet against the source MAC address in the Ethernet
header
GC
ip dhcp snooping vlan Enables DHCP snooping on the specified VLAN GC
ip dhcp snooping information
option circuit-id
Specifies DHCP Option 82 circuit-id suboption
information
IC
ip dhcp snooping trust Configures the specified interface as trusted IC
clear ip dhcp snooping
binding
Clears DHCP snooping binding table entries from RAM PE
clear ip dhcp snooping
database flash
Removes all dynamically learned snooping entries from
flash memory.
PE
ip dhcp snooping database
flash
Writes all dynamically learned snooping entries to flash
memory
PE
show ip dhcp snooping Shows the DHCP snooping configuration settings PE
show ip dhcp snooping
binding
Shows the DHCP snooping binding table entries PE
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