peer tracking (BGP multi-instance VPN instance IPv4 address family view) (group)

Function

The peer tracking command enables BGP Peer Tracking. That is, you can configure BGP to fast detect the unreachable state of a peer and re-establish the connection between the local device and the peer.

The undo peer tracking command disables BGP Peer Tracking.

By default, BGP Peer Tracking is disabled.

Format

peer group-name tracking [ delay delay-time ]

undo peer group-name tracking

Parameters

Parameter	Description	Value
group-name	Specifies the name of a peer group.	The name is a string of 1 to 47 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string.
delay delay-time	Indicates the interval between when BGP detects the peer unreachable and when BGP tears down the corresponding connection.	The value is an integer that ranges from 0 to 65535, in seconds. The default value is 0 seconds.

Parameter

Description

Value

group-name

Specifies the name of a peer group.

The name is a string of 1 to 47 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string.

delay delay-time

Indicates the interval between when BGP detects the peer unreachable and when BGP tears down the corresponding connection.

The value is an integer that ranges from 0 to 65535, in seconds. The default value is 0 seconds.

Views

BGP multi-instance VPN instance IPv4 address family view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
bgp	write

Usage Guidelines

Usage Scenario

In a network where BFD is unsuitable to be deployed, you can configure BGP Peer Tracking on the local device to implement fast network convergence by rapidly detecting the unreachable state of the peer.

A BGP peer is considered unreachable in either of the following situations:

The BGP peer's IP address does not match any route in the IP routing table.
The BGP peer's IP address matches a route with the outbound interface being a Null0 interface in the IP routing table.
A proper value of delay-time can ensure network stability when a peer is detected unreachable.
If delay-time is set to 0, BGP immediately tears down the connection between the local device and its peer after the peer is detected unreachable.
If IGP route flapping occurs and delay-time for an IBGP peer is set to 0, the peer relationship between the local device and the peer alternates between Up and Down. Therefore, delay-time for an IBGP peer should be set to a value greater than the actual IGP route convergence time.
When BGP neighbors successfully perform the GR negotiation, the master/slave switchover occurs on the BGP neighbors, to prevent the failure of GR, delay-time should be set to a value greater than GR convergence time. If delay-time is set to be smaller than the GR convergence time, the connection between the local device and the BGP peer will be torn down, which leads to the failure of GR.

Prerequisites

The peer as-number command has been used to create a peer group.

Precautions

IGP is configured with GR, and the BGP neighbor relationship is established based on IGP routes. In such a situation, when a node fails on the network and the master/slave switchover occurs on the node, IGP does not delete the routes from the node, and BGP neighbors cannot sense the fault on the node. Therefore, the BGP Peer Tracking function does not take effect.

Example

# Configure BGP Peer Tracking.

<HUAWEI> system-view
[~HUAWEI] ip vpn-instance vpna
[*HUAWEI-vpn-instance-vpna] ipv4-family
[*HUAWEI-vpn-instance-vpna-af-ipv4] route-distinguisher 100:1
[*HUAWEI-vpn-instance-vpna-af-ipv4] vpn-target 111:1 both
[*HUAWEI-vpn-instance-vpna-af-ipv4] quit
[*HUAWEI-instance-vpna] quit
[*HUAWEI] bgp 100 instance a
[*HUAWEI-bgp-instance-a] ipv4-family vpn-instance vpna
[*HUAWEI-bgp-instance-a-vpna] group test
[*HUAWEI-bgp-instance-a-vpna] peer test tracking