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What is BFD echo function?
The BFD echo function sends echo packets from the forwarding engine to the remote BFD neighbor. BFD can use the slow timer to slow down the asynchronous session when the echo function is enabled and reduce the number of BFD control packets that are sent between two BFD neighbors.
What is a BFD packet?
The Bidirectional Forwarding Detection (BFD) protocol is a simple hello mechanism that detects failures in a network. Hello packets are sent at a specified, regular interval. A neighbor failure is detected when the routing device stops receiving a reply after a specified interval.
How does BFD protocol work?
BFD provides a method to validate the operation of the forwarding plane between two routers. Upon detecting a failure, triggers an action in a routing protocol (severing a session or adjacency). In either mode, BFD provides an Echo function in which one side can request its neighbor to loop back a series of packets.
How do I disable BFD?
To enter Bidirectional Forwarding Detection (BFD) configuration mode, use the bfd command in global configuration mode. To exit BFD configuration mode and return to global configuration mode, use the no form of this command.
What is advantage of using BFD?
There are several advantages to implementing BFD over reduced timer mechanisms for routing protocols: Although reducing the EIGRP, IS-IS, and OSPF timers can result in minimum detection timer of one to two seconds, BFD can provide failure detection in less than one second.
What is the advantage of BFD?
Does BFD need to be configured on both sides?
BFD Operation Cisco supports the BFD asynchronous mode, which depends on the sending of BFD control packets between two systems to activate and maintain BFD neighbor sessions between routers. Therefore, in order for a BFD session to be created, you must configure BFD on both systems (or BFD peers).
What is BFD fast detect?
BFD (Bidirectional Forwarding Detection) is a super-fast protocol that is able to detect link failures within milliseconds or even microseconds. All (routing) protocols have some sort of mechanism to detect link failures. OSPF uses hello packets and a dead interval, EIGRP uses hello packets and a hold-down timer, etc.
Where does the BFD echo function send the packets?
The Nexus documentation now says “ The BFD echo function sends echo packets from the forwarding engine to the remote BFD neighbor. The BFD neighbor forwards the echo packet back along the same path in order to perform detection; the BFD neighbor does not participate in the actual forwarding of the echo packets.” The RFC says something similar.
What is the BFD control packet failure detection time?
BFD control packet failure detection time. This is the maximum amount of time that can elapse without receipt of a BFD control packet before the session is declared down. Minimum period between sending of BFD echo packets. Value of ( I x M) x M —BFD echo packet failure detection time.
How is a BFD control packet sent in an encapsulation?
Generic BFD Control Packet Format BFD Control packets are sent in an encapsulation appropriate to the environment. The specific encapsulation is outside of the scope of this specification. See the appropriate application document for encapsulation details. The BFD Control packet has a Mandatory Section and an optional Authentication Section.
What is the source port for Cisco BFD?
For single-hop situations, RFC 5881 applies: “BFD Control packets MUST be transmitted in UDP packets with destination port 3784, within an IPv4 or IPv6 packet. The source port MUST be in the range 49152 through 65535.” Cisco BFD follows that specification, per various Cisco documents.