ospf bfd

Function

The ospf bfd command enables the bidirectional forwarding detection (BFD) on the specified interface enabled with OSPF, or sets the parameter values of a BFD session.

The undo ospf bfd command deletes the BFD on the specified interface, or restores the default parameter values of a BFD session.

By default, BFD is not enabled or configured in the OSPF interface view.

Format

ospf bfd enable

ospf bfd { min-rx-interval receive-interval | min-tx-interval transmit-interval | detect-multiplier multiplier-value } ^*

undo ospf bfd enable

undo ospf bfd { min-rx-interval [ receive-interval ] | min-tx-interval [ transmit-interval ] | detect-multiplier [ multiplier-value ] } ^*

Parameters

Parameter	Description	Value
enable	Enables BFD.	-
min-rx-interval receive-interval	Indicates the minimum interval for receiving BFD packets from the neighbor.	The value is an integer ranging from 100 to 1000, in milliseconds. The default value is 1000.
min-tx-interval transmit-interval	Indicates the minimum interval for sending BFD packets to the neighbor.	The value is an integer ranging from 100 to 1000, in milliseconds. The default value is 1000.
detect-multiplier multiplier-value	Indicates the local detection multiplier. NOTE: After BFD is enabled, OSPF establishes BFD sessions only with neighbors in the Full state. For different products, the maximum, minimum and the default values just mentioned may vary.	The value of the multiplier-value ranges from 3 to 50. By default, the value is 3.

Views

Ethernet interface view, Ethernet sub-interface view, Eth-Trunk interface view, Eth-Trunk sub-interface view, Tunnel interface view, Dialer interface view, VLANIF interface view, Virtual-Template interface view, BDIF interface view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

A link fault or a topology change causes devices to recalculate routes. Therefore, the convergence of routing protocols must be as fast as possible to improve network performance.

Link faults are inevitable. Therefore, quickly detecting faults and notifying routing protocols of the faults is a feasible solution to immediately rectify link faults. If BFD is associated with routing protocols, BFD can speed up the convergence of routing protocols when a link fault occurs.

After OSPF establishes a BFD session, the default parameter value is used. BFD session parameters can also be modified as required.

Actual interval at which BFD packets are transmitted on the local devices = Max { configured interval transmit-interval at which BFD packets are transmitted, configured interval receive-interval at which BFD packets are received on the peer device }
Actual interval at which BFD packets are received on the local devices = Max { configured interval transmit-interval at which BFD packets are transmitted on the peer device, configured interval receive-interval at which BFD packets are received on the local device }
Actual time for detecting BFD packets = Actual interval at which BFD packets are received on the local device x Configured detection multiplier multiplier-value

For example:

On the local device, the configured interval at which BFD packets are transmitted is 200 ms; the interval at which BFD packets are received is set to 300 ms; the detection multiplier is 4.
On the peer device, the configured interval at which BFD packets are transmitted is 100 ms; the interval at which BFD packets are received is 600 ms; the detection multiplier is 5.

Then:

On the local device, the actual interval at which BFD packets are transmitted is 600 ms calculated by using the formula max {200 ms, 600 ms}; the interval at which BFD packets are received is 300 ms calculated by using the formula max {100 ms, 300 ms}; the detection period is 1500 ms calculated by multiplying 300 ms by 5.
On the peer device, the actual interval at which BFD packets are transmitted is 300 ms calculated by using the formula max {100 ms, 300 ms}, the actual interval at which BFD packets are received is 600 ms calculated by using the formula max {200 ms, 600 ms}, and the detection period is 2400 ms calculated by multiplying 600 ms by 4.

Prerequisites

The set BFD session parameters take effect only when BFD is enabled on the interface.

Configuration Impact

If the global BFD is not configured, BFD on the interface can be configured but the BFD session cannot be set up. Similarly, if the parameters of a BFD session are set but the ospf bfd enable command is not configured, the BFD session cannot be set up.

The priority of BFD configured on an interface is higher than what is configured in the process. If the BFD is enabled on the interface, the BFD session is set up by using the parameters of the BFD configured on the interface.

Precautions

After BFD is configured, OSPF establishes BFD sessions only with neighbors.
The ospf bfd enable command and the ospf bfd block command are mutually exclusive.
After BFD is disabled on the interface using the undo ospf bfd enable command, the configurations of the parameters of the BFD session on the interface still exist.

Example

# Enable BFD on GigabitEthernet 0/0/1 and then set the minimum receiving interval to 400 ms and the local detection multiplier to 4.

<sysname> system-view
[sysname] interface GigabitEthernet 0/0/1
[sysname-GigabitEthernet0/0/1] ospf bfd enable
[sysname-GigabitEthernet0/0/1] ospf bfd min-rx-interval 400 detect-multiplier 4

# Delete the BFD of GigabitEthernet 0/0/1.

<sysname> system-view
[sysname] interface GigabitEthernet 0/0/1
[sysname-GigabitEthernet0/0/1] undo ospf bfd enable