Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 409

Valid ARP Replies Invalid ARP Requests Invalid ARP Replies Dell# : 1000 : 1000 : 0 Bypassing the ARP Inspection You can configure a port to skip ARP inspection by defining the interface as trusted, which is useful in multiswitch environments. ARPs received on trusted ports bypass validation against the binding table. All ports are untrusted by default. To bypass the ARP inspection, use the following command. • Specify an interface as trusted so that ARPs are not validated against the binding table. INTERFACE mode arp inspection-trust DAI is supported on Layer 2 and Layer 3. Source Address Validation Using the DHCP binding table, Dell Networking OS can perform three types of source address validation (SAV). Table 26. Three Types of Source Address Validation Source Address Validation IP Source Address Validation DHCP MAC Source Address Validation IP+MAC Source Address Validation Description Prevents IP spoofing by forwarding only IP packets that have been validated against the DHCP binding table. Verifies a DHCP packet's source hardware address matches the client hardware address field (CHADDR) in the payload. Verifies that the IP source address and MAC source address are a legitimate pair. 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 or the port channel interface on which the requesting client is attached and the VLAN the client belongs to. 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 and optionally that the client belongs to the permissible VLAN. If an attacker is Dynamic Host Configuration Protocol (DHCP) 409