Dell N3200-ON Networking N-Series Switches CLI Reference Guide version 6.8.0 - Page 1920

When allow-default is set in loose mode (any), if the source IP address is not found but a default route is present in the table, the uRPF check will pass. When allow-default is set in strict mode (rx), it will prevent the incoming packet's source IP address to have a route out of a different interface than received. The strict mode option with the default route is used typically on the upstream interface. Default Configuration By default uRPF checking is disabled on interfaces. Command Mode Interface (Ethernet) Configuration mode User Guidelines In any mode, a check is performed to see if the source address is reachable in the routing table and, if found, the packet is forwarded. In rx mode, a check is performed to see if the source address is reachable in the routing table via the same interface on which the packet was received. If both conditions are met, the packet is forwarded. The allow-default option can be set in conjunction with strict and loose modes. It will include IP addresses not specifically contained in the routing table in the uRPF check. In loose mode, if the source ip address is not found but a default route is present in the table, the uRPF check will allow the packet to be routed. In strict mode, it will drop incoming packets where the route to the packets source IP address is on an interface other than the interface on which the packet was received. The strict mode option with the allow-default option is used typically on upstream interfaces. Command History Command introduced in version 6.6 firmware. Example console#configure console(config)#system urpf enable console(config)#interface gi1/0/7 console(config-Gi1/0/7)#routing Layer 3 Routing Commands 1920