The multi-hop command configures the number of the default destination port for the multi-hop BFD control packet.
The undo multi-hop command restores the destination port number of the multi-hop BFD control packet to the default value.
| Parameter | Description | Value |
|---|---|---|
| 3784 | Indicates that destination port 3784 is used for the multi-hop BFD control packet. | - |
| 4784 | Indicates that destination port 4784 is used for the multi-hop BFD control packet. | - |
By default, destination port 3784 is used for the multi-hop BFD control packet.
According to the BFD draft, 4784 is the destination port number of multi-hop BFD session packets.
During interworking with devices of earlier versions, the FW chooses 3784 as the destination port number of multi-hop BFD session packets. During interworking with the devices of other vendors, the FW uses 4784 as the destination port number of multi-hop BFD session packets.
If destination port 4784 is used for the multi-hop BFD control packet on a router, the router fails to negotiate with the router on which destination port 3784 is used for the multi-hop BFD control packet.
If destination port 3784 is used for the multi-hop BFD control packet on a router, the router can successfully negotiate with the router on which destination port 4784 is used for the multi-hop BFD control packet. At the same time, on the router that is configured with destination port 3784, destination port 3784 is automatically updated to destination port 4784.
If destination port 3784 is used in 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, it may take a long time to update the destination ports. Therefore, when the interval for configuring multi-hop BFD sessions is set to a small value, the system prompts that the BFD session is being updated and you may try later.
When the number of the destination port used for the multi-hop BFD control packet is updated, the BFD session in the Up state may change to Down, and then the BFD session is renegotiated.