multi-hop

Function

The multi-hop command configures the destination port number for a multi-hop BFD session.

The undo multi-hop command restores the default destination port number for a multi-hop BFD session.

By default, destination port 3784 is used in multi-hop BFD control packets.

Format

multi-hop destination-port { 3784 | 4784 }

undo multi-hop destination-port

Parameters

Parameter	Description	Value
3784	Indicates that destination port 3784 is used in multi-hop BFD control packets.	-
4784	Indicates that destination port 4784 is used in multi-hop BFD control packets.	-

Views

BFD view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

As defined in the BFD draft, destination port 4784 is used by multi-hop BFD control packets. When the device running the latest version interworks with devices running earlier versions, destination port 3784 is used by multi-hop BFD control packets. When the device interworks with non-Huawei devices, destination port 4784 is used by multi-hop BFD control packets.

Precautions

If destination port 4784 is used by multi-hop BFD control packets, the device fails to negotiate with the remote device on which destination port 3784 is used by multi-hop BFD control packets.
If destination port 3784 is used by multi-hop BFD control packets, the device can successfully negotiate with the remote device on which destination port 4784 is used by multi-hop BFD control packets. On the device that is configured with destination port 3784, destination port 3784 is automatically updated to destination port 4784.
If destination port 3784 is used by both multi-hop and single-hop BFD control packets, the single-hop and multi-hop BFD control packets are processed according to their TTLs.
When a large number of multi-hop BFD sessions are set up, updating the destination ports may take a long time. Therefore, when a smaller interval for configuring multi-hop BFD sessions is used, the system displays a message indicating that the BFD session is being updated and you may try later.
When the number of the destination port used in a multi-hop BFD control packet is updated, the BFD session in Up state may change to Down and then the BFD session is renegotiated.

Determine to use port 3784 or 4784 before configuring a multi-hop BFD session between a Huawei device and a non-Huawei device. If the port number is not specified, you must change the port number after the BFD session becomes Up. Before changing the port number, shut down the BFD session. This is because changing the port number may cause all multi-hop BFD session to flap and affect services.

Example

# Set the default destination port number to 4784 for multi-hop BFD control packets.

<HUAWEI> system-view
[HUAWEI] bfd
[HUAWEI-bfd] multi-hop destination-port 4784