Information
DHCP snooping protects the network from common DHCP attacks, including address spoofing resultingfrom a rogue DHCP server operating on the network or exhaustion of addresses on a DHCP servercaused by mass address requests by an attacker on the network. DHCP snooping designates trustedDHCP servers and ports on which DHCP requests and responses are accepted.
DHCP Snooping classifies switch ports as either trusted or untrusted.Trusted ports are those connected to legitimate DHCP servers.Untrusted ports are typically edge ports connected to end devices or untrusted networks.The switch inspects DHCP messages and allows only valid responses from trusted ports. Malicious or unauthorized DHCP responses from untrusted ports are dropped.
Solution
The following is a DHCPv4-snooping sample configuration -
switch(config)# dhcpv4-snooping
switch(config)# vlan <vlan-id>
switch(config-vlan-id)# dhcpv4-snooping
switch(config-vlan-id)# exit
switch(config)#
switch(config)# interface <trusted interface id>
switch(config-if)# dhcpv4-snooping trust
switch(config-if)# exit
switch(config)# dhcpv4-snooping authorized-server <ipv4-server-address> vrf <vrf-name>
The following is a DHCPv6-snooping sample configuration:
switch(config)# dhcpv6-snooping
switch(config)# vlan <vlan-id>
switch(config-vlan-id)# dhcpv6-snooping
switch(config-vlan-id)# exit
switch(config)#
switch(config)# interface <trusted interface id>
switch(config-if)# dhcpv6-snooping trust
switch(config-if)# exit
switch(config)# dhcpv6-snooping authorized-server <ipv6-server-address> vrf <vrf-name>
Impact:
Prevents rogue DHCP servers from assigning incorrect or malicious IP configuration to clients.Protects against DHCP-based man-in-the-middle attacks.
Item Details
Category: ACCESS CONTROL, SECURITY ASSESSMENT AND AUTHORIZATION, RISK ASSESSMENT, SYSTEM AND COMMUNICATIONS PROTECTION, SYSTEM AND INFORMATION INTEGRITY
References: 800-53|AC-17, 800-53|AC-17(1), 800-53|CA-9, 800-53|RA-5, 800-53|SC-7, 800-53|SC-7(5), 800-53|SI-4, CSCv7|12.2, CSCv7|12.4
Control ID: 1d4ece56264348d3bd5362eee327a261209a071b22d2a70a3ff9ea6f5d6ba0fd