Configuration manual

Enabling IP Source Address Validation
IP source address validation (SAV) prevents IP spoofing by forwarding only IP packets that have been
validated against the DHCP binding table.
A spoofed IP packet is one in which the IP source address is strategically chosen to disguise the attacker.
For example, using ARP spoofing, an attacker can assume a legitimate client’s identity and receive traffic
addressed to it. Then the attacker can spoof the client’s IP address to interact with other clients.
The DHCP binding table associates addresses the DHCP servers assign, with the port on which the
requesting client is attached. When you enable IP source address validation on a port, the system verifies
that the source IP address is one that is associated with the incoming port. If an attacker is impostering as
a legitimate client, the source address appears on the wrong ingress port and the system drops the
packet. Likewise, if the IP address is fake, the address is not on the list of permissible addresses for the
port and the packet is dropped.
To enable IP source address validation, use the following command.
• Enable IP source address validation.
INTERFACE mode
ip dhcp source-address-validation
DHCP MAC Source Address Validation
DHCP MAC source address validation (SAV) validates a DHCP packet’s source hardware address against
the client hardware address field (CHADDR) in the payload.
The Dell Networking OS version 8.2.1.1 ensures that the packet’s source MAC address is checked against
the CHADDR field in the DHCP header only for packets from snooped VLANs.
• Enable DHCP MAC SAV.
CONFIGURATION mode
ip dhcp snooping verify mac-address
Enabling IP+MAC Source Address Validation
IP source address validation (SAV) validates the IP source address of an incoming packet against the
DHCP snooping binding table.
IP+MAC SAV ensures that the IP source address and MAC source address are a legitimate pair, rather than
validating each attribute individually. You cannot configure IP+MAC SAV with IP SAV.
1. Allocate at least one FP block to the ipmacacl CAM region.
CONFIGURATION mode
cam-acl l2acl
2. Save the running-config to the startup-config.
EXEC Privilege mode
copy running-config startup-config
3. Reload the system.
EXEC Privilege
reload
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Dynamic Host Configuration Protocol (DHCP)