Echo Function

The Echo function is used to test the forwarding plane of the neighbor. Echo packets are formatted such that the neighbor‘s forwarding plane redirects the packet back to the sender. The Echo function is enabled by default, and may be used in both operating modes; asynchronous and demand. While in asynchronous mode, the BFD probe session overrides the minimum receive interval, using the slow-timer‘s configured value, to inform the neighbor to reduce the rate of control packet transmission. If the BFD probe session is in demand mode, the Echo function is the only means of determining the liveliness of the neighbor, as the neighbor does not transmit periodic control packets.

The Echo function provides three configurable attributes the user may modify in the BFD probe configuration mode:

• The minimum transmit interval, configurable in 50ms increments, defines how quickly the echo packets are transmitted
• The minimum receive interval, configurable in 50ms increments, informs the neighbor how quickly it may transmit echo packets
• The missed packet count determines how many transmitted echo packets may be lost before the BFD probe session transitions to the down state

Use the no echo-mode command, in BFD probe configuration mode, to disable the Echo function for BFD sessions.

This example shows how to disable the Echo function for BFD session bfdProbe1:

System(rw)->configure
System(rw-config)->probe bfdProbe1 bfd
System(su-config-probe-bfd)->no echo-mode
System(su-config-probe-bfd)->

Use the echo command, in BFD probe configuration mode, to modify Echo packet parameters for BFD sessions.

This example shows how to set the minimum transmit and receive intervals to 350ms and the minimum number of missed consecutive Echo packets to 5 for BFD probe bfdProbe1:

System(rw)->configure
System(rw-config)->probe bfdProbe1 bfd
System(su-config-probe-bfd)->echo min-tx 350 min-rx 350 miss-count 5
System(su-config-probe-bfd)->