BFD is a detection protocol designed to provide fast forwarding path failure detection times for all media types, encapsulations, topologies, and routing protocols. In addition to fast forwarding path failure detection, BFD provides a consistent failure detection method for network administrators. BFD provides fast peer failure detection times independently of all media types, encapsulations, topologies, and routing protocols, including BGP, EIGRP, IS-IS, and OSPF. By sending rapid failure detection notices to the routing protocols in the local router to initiate the routing table recalculation process, BFD contributes to greatly reduced overall network convergence time.

There are several benefits to using BFD over reducing timer mechanisms for routing protocols:

• Although reducing the EIGRP, IS-IS, and OSPF timers can result in a minimum detection timer of one to two seconds, BFD can provide failure detection in less than one second.
• Because BFD is not tied to any particular routing protocol, it can be used as a generic and consistent failure detection mechanism for EIGRP, IS-IS, and OSPF.
• Because some parts of BFD can be distributed to the data plane, it can be less CPU-intensive than the reduced EIGRP, IS-IS, and OSPF timers, which exist wholly at the control plane.

Graceful Restart and Non-Stop Routing

Graceful Restart (GR)—also known as Non-Stop Forwarding (NSF)—and Non-Stop Routing (NSR) are two different mechanisms to prevent routing protocol reconvergence during a processor switchover. Graceful Restart and Non-Stop Routing suppress routing changes on peers to Stateful Switchover (SSO)–enabled devices during processor switchover events of SSO, reducing network instability and downtime. Graceful Restart and NSR both allow for the forwarding of data packets to continue along known routes while the routing protocol information is being restored (in the case of GR) or refreshed (in the case of NSR) following a processor switchover. GR is available for OSPF, ISIS, EIGRP, LDP, and BGP. NSR is available in Cisco IOS for ISIS and BGP. Compared to GR, NSR uses more system resources due to the information transfer to the standby processor.

Virtual Routing and Forwarding (VRF)

Virtual routing and forwarding (VRF) is a technology that supports multiple routing instances inside a single router or Layer 3 switch. With VRF, a single router can have multiple separate routing tables, all completely isolated from each other. One or more logical or physical interfaces may have a VRF instance, and these VRF instances do not share routes; therefore, the packets are only forwarded between interfaces on the same VRF instance.

VRF instances are the TCP/IP Layer 3 equivalent of VLANs. Because the routing instances are independent, the same or overlapping IP addresses can be used without conflicting with each other. Network functionality is improved because network paths can be segmented without requiring multiple routers.

VRF instances are used to provide network segmentation, such as to separate business traffic from process control traffic in plants. Because VRF allows for true routing and forwarding separation, dedicated data and control planes are defined to handle traffic belonging to groups with various requirements or policies. This provides an additional level of segregation and security because no communication between devices belonging to different VRF instances is allowed unless explicitly configured.