Which of the following commands must be present in the configuration to support Unicast RFP?
- ip cef
- ip route 0.0.0.0 0.0.0.0
The command ip cef must be present in the configuration to support Unicast Reverse Path Forwarding (RPF). If the router is set to its defaults, it will be present. Unicasts RPF uses the tables created by CEF to validate packet source addresses. Therefore, it must be enabled. Unicast RPF can be enabled in three modes:
Strict mode – The source address must be must be reachable on the interface where the packet arrived.
Loose mode – Traffic is allowed if the source address is reachable via any interface on the router as indicted in the routing table.
VRF mode – Evaluates an incoming packet’s source IP address against the VRF table configured for an eBGP neighbor.
The bandwidth command, while desirable to ensure proper cost calculation of the interface for routing purposes, is not a requirement for Unicast RPF.
The ip route 0.0.0.0 0.0.0 command creates a default route. A default route does not need to be present for Unicast RPF to function.
The log command is not required. This command should be used with caution with any access list, as it causes an increase in CPU usage in the router.
Configure and verify router security features