bfd bind one-arm-echo

Function

The bfd bind one-arm-echo command creates a one-arm BFD echo session.

By default, no one-arm BFD echo session is created.

Format

bfd sessname-value bind peer-ip ip-address [ vpn-instance vpn-name ] interface { interface-name | interface-type interface-number } [ source-ip ip-address ] one-arm-echo

bfd sessname-value bind peer-ipv6 ipv6-address [ vpn-instance vpn-name ] interface { interface-name | interface-type interface-number } [ source-ipv6 ipv6-address ] one-arm-echo

Parameters

Parameter	Description	Value
sessname-value	Specifies the name of a one-arm BFD echo session.	The value is a string of 1 to 64 characters, spaces not supported. When quotation marks are used around the string, spaces are allowed in the string. When the name of a BFD session is configured, the uppercase and lowercase letters in the name must be the same as what you enter. BFD session names are case-insensitive. For example, ABC and abc are regarded as the same BFD session. If you have configured ABC as the name of a BFD session, the ABC BFD session view is directly displayed when you configure abc.
peer-ip ip-address	Specifies the peer IPv4 address bound to a one-arm BFD echo session.	The value is in dotted decimal notation.
vpn-instance vpn-name	Specifies the name of the VPN instance bound to a one-arm BFD echo session.	The value is a string of 1 to 31 case-sensitive characters, spaces not supported. In addition, the VPN instance name must not be _public_. When double quotation marks are used around the string, spaces are allowed in the string.
interface interface-type interface-number	Specifies the type and number of the local Layer 3 interface bound to a one-arm BFD echo session.	-
source-ip ip-address	Specifies the source IPv4 address carried in BFD packets. If this parameter is not specified, the system searches the local routing table for the IP address of an outbound interface connected to the remote end and uses the IP address as the source IP address before sending BFD packets. This parameter usually does not need to be specified.	The value is in dotted decimal notation.
one-arm-echo	Indicates a one-arm BFD echo session.	-
destination-ip ip-address	Specifies the destination IPv4 address of BFD packets.	The value is in dotted decimal notation.
peer-ipv6 ipv6-address	Specifies the peer IPv6 address bound to a BFD for IPv6 session.	The value is a 32-bit hexadecimal number in the format of X:X:X:X:X:X:X:X.
source-ipv6 ipv6-address	Specifies the source IPv6 address carried in a BFD packet. If you do not specify the source IP address, the system automatically sets the source IP address according to the following rules: During BFD for IPv6 session negotiation, if the source IPv6 address is not specified, the system searches the local routing table for an outbound interface from which the peer IP address is reachable. The IPv6 address of this outbound interface is used as the source IP address of the BFD packets sent by the local end. If this parameter is not specified when a BFD for IPv6 session is detecting links, the system uses a fixed source IPv6 address in BFD packets. Generally, you do not need to set this parameter. When BFD is used with Unicast Reverse Path Forwarding (URPF), you must manually configure the source IPv6 address in BFD packets because URPF checks the source IPv6 address in received packets.	The value is a 32-bit hexadecimal number in the format of X:X:X:X:X:X:X:X.
destination-ipv6 ipv6-address	Specifies the destination IPv6 address of BFD packets.	The value is a string of case-sensitive characters. It cannot contain spaces.

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
bfd	write

Usage Guidelines

Usage Scenario

Among two interconnected devices, one device supports BFD, and the other device does not support BFD. To quickly detect link faults, you can create a one-arm BFD Echo session on the device that supports BFD. After receiving a BFD Echo packet, the device that does not support BFD immediately loops back the packet for quick link fault detection.

When a one-arm BFD Echo session is created:

The source-ip parameter is configured to ensure that BFD packets are not incorrectly discarded when Unicast Reverse Path Forwarding (URPF) is enabled. Ensure that the source IP address is correct. The system only checks whether the source IP address is valid (for example, it cannot be a multicast or broadcast address) without checking its correctness.
If the source-ip parameter is specified, the system searches for the outbound interface of the route based on the peer-ip parameter to obtain the destination address of the BFD packet to be sent. The source address is the value specified by the source-ip parameter.
If the source-ip parameter is not specified, the system searches the routing table for the outbound interface address based on the peer-ip parameter and uses the outbound interface address as the source and destination addresses in BFD packets.

Prerequisites

BFD has been globally enabled using the bfd command in the system view.

Precautions

The differences between a one-arm BFD echo session and a common BFD session are as follows:

When creating a one-arm BFD echo session, you need to specify only the local parameter in the discriminator command.
You can run only the min-echo-rx-interval command to change the minimum interval at which one-arm BFD echo session packets are received.
After a one-arm BFD echo session is created, changing the IP address of the outbound interface for BFD packets does not change the source IP address carried in the BFD packets.
One-arm BFD echo sessions can apply only to single-hop detection.
If the destination-ip parameter is specified, the incoming and outgoing paths of packets may be inconsistent. If the incoming path fails, the status of the one-arm-echo BFD session may be incorrectly set to down.
You can run the undo bfd session-name command to delete a specified BFD session and its binding information.

Example

# Create a one-arm BFD echo session named test.

<HUAWEI> system-view
[~HUAWEI] bfd
[*HUAWEI-bfd] quit
[*HUAWEI] interface GigabitEthernet 0/1/0
[*HUAWEI-GigabitEthernet0/1/0] ip address 10.1.1.2 24
[*HUAWEI-GigabitEthernet0/1/0] quit
[*HUAWEI] bfd test bind peer-ip 10.1.1.1 interface GigabitEthernet0/1/0 one-arm-echo