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layer2-liveness-detection (Send)

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 17.4R1.

Description

Configure a router acting as a broadband network gateway (BNG) to conduct a host connectivity check on its directly connected DHCPv4 and DHCPv6 clients to determine the validity and state of the DHCP client session, and to clean up inactive sessions.

The BNG sends ARP or ND request packets to the each DHCP client at a configurable interval, then waits for a response. If it receives a response from a client before the interval times out, it sends another request to the client when the timer expires.

If the BNG does not receive a response before the interval times out, it sets the timer to 30 seconds and sends another request. This is the first retry attempt.

If it receives a response from a client before the 30-second interval times out, it sends another request to the client when the timer expires. If the 30-second timer expires before a response is received, the BNG sets the timer to 10 seconds and sends another request. This is the second retry attempt. If the BNG does not receive a response within this interval it resets the timer to 10 seconds and sends another request. The BNG continues to send requests at 10-second intervals until it either receives a response from the client before the interval times out or exhausts the number of retry attempts.

The first retry attempt uses a 30-second interval. Subsequent retries occur at 10-second intervals. The number of possible 10-second retries is therefore the total number of retries minus 1. For example, if you configure 5 retries, there is one 30-second retry and up to four 10-second retries.

If the BNG attempts all the retries and never receives a response from a client within the interval, the client session is declared to be down.

Note

The only option to the failure-action statement supported by Layer 2 liveness detection is clear-binding.

Options

max-consecutive-retries numberMaximum number of consecutive times that the router sends an ARP request packet in the absence of an ARP response packet.

Range: 3 through 6 retries

Default: 3 retries

transmit-interval secondsInitial interval that the router waits for an ARP response after sending an ARP request packet to the client or waits for an ND response packet after sending an NG request packet to the client.

Range: 300 through 1800 seconds

Default: 300 seconds

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.