pim ipv6 bfd

Usage Scenario

To minimize the impact of a fault on services and improve network availability, a network device is required to fast detect a communication fault between adjacent devices so that the upper layer protocol can rectify the fault to ensure normal services.

In multicast applications, if the current Designated router (DR) or Assert winner at the shared network segment is faulty, other PIM neighbors start a new DR election or Assert election after the neighbor relationship or the Assert timer times out. Consequently, multicast data transmission is discontinued. The discontinue period, usually in seconds, is longer than the timeout period of the neighbor relationship or the Assert timer.

BFD can detect the status of the link at the shared network segment within milliseconds and fast respond to the fault on the PIM neighbor. If the interface configured with BFD for IPv6 PIM does not receive any BFD packets from the current DR or Assert winner within a detection period, it considers that a fault occurs on the current DR or Assert winner. BFD fast notifies the Routing Management (RM) of the session status and the RM then notifies PIM of the session status. PIM triggers a new DR election or Assert election immediately rather than waits until the neighbor relationship or the Assert timer times out. This reduces the discontinue period of multicast data transmission and thus improves the reliability of multicast data transmission.

If you need to control detection parameters of PIM IPv6 BFD packets, run the pim ipv6 bfd command to configure the sending interval, receiving interval, and local detection multiplier for PIM IPv6 BFD packets.min-tx-interval, min-rx-interval, and detect-multiplier parameters can be configured separately on two ends, that is, the two link ends can send or receive BFD packets at different rates. If there is no special requirement for the detection period and the link is stable, you are recommended to configure the same parameter values for the routing devices of the same performance at the shared network segment.

Prerequisites

The multicast ipv6 routing-enable command is run in the public network instance view.

BFD for IPv6 PIM depends on the BFD protocol. Therefore, you need first to enable BFD globally to validate the BFD for IPv6 PIM function.

Before configuring BFD for IPv6 PIM, enable IPv6 PIM-SM in the interface view. If the undo pim ipv6 sm command is run, IPv6 PIM-SM is disabled and the BFD for IPv6 PIM function is removed from the interface at the same time.

The pim ipv6 bfd command and the pim ipv6 bfd enable command need to be used together. To validate PIM IPv6 BFD, ensure that a BFD session has been set up and the session is in the Up state.

Configuration Impact

The PIM IPv6 BFD parameters setting by using the pim ipv6 bfd command take effect only after the pim ipv6 bfd enable command is run.

After BFD parameters are configured, PIM provides the address to be detected, minimum sending interval and receiving interval of PIM IPv6 BFD packets, and local detection multiplier for BFD. The two ends enabled with BFD then negotiate the actual sending interval and receiving interval, and the detection period based on these configured parameters. During the detection phase, BFD notifies the RM of the BFD session status and the RM then notifies PIM of the session status.If a link fault occurs, BFD fast notifies the RM of the session status and the RM then notifies PIM of the session status. The PIM protocol deletes the status of the faulty interface, triggers a new DR or Assert election, and restores the forwarding of multicast data to the downstream interface. This shortens the period of multicast traffic interruption caused by the interface fault.

Precautions