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Enabling Dedicated and Real-Time BFD on SRX Devices

By default, SRX Series devices operate in centralized BFD mode. They also support distributed BFD, dedicated BFD, and real-time BFD.

Dedicated BFD

Enabling dedicated BFD impacts traffic throughput as one CPU core is removed from data plane processing.

To enable dedicated BFD on the SRX100, SRX110, SRX210, SRX220, SRX240, SRX300, SRX320, SRX340, SRX345, SRX380, SRX550, SRX550M, SRX650, and SRX1500 devices:

  1. Include the dedicated-ukern-cpu statement at the [edit chassis] hierarchy level and then commit the configuration.

    1. [edit]

    2. user@host# set chassis dedicated-ukern-cpu

      user@host# commit

      The following warning message to reboot the system displays when you commit the configuration:

      warning: Packet processing throughput may be impacted in dedicated-ukernel-cpu mode. warning: A reboot is required for dedicated-ukernel-cpu mode to be enabled. Please use "request system reboot" to reboot the system. commit complete

  2. Reboot the device to enable the configuration:

    1. user@host> request system reboot

  3. Verify that dedicated BFD is enabled.

    user@host> show chassis dedicated-ukern-cpu

    Dedicated Ukern CPU Status: Enabled

Real-Time BFD

Enabling real-time BFD does not impact data plane performance. Higher priority is given to the Packet Forwarding Engine process handling BFD in distributed mode. This is suitable for scenarios where there are fewer BFD sessions.

Note:

For more information about BFD in distributed mode, see Understanding How BFD Detects Network Failures.

To enable real-time BFD on SRX100, SRX110, SRX210, SRX220, SRX240, SRX300, SRX320, SRX340, SRX345, SRX550, SRX550M, and SRX650 devices:

  1. Include the realtime-ukern-thread statement at the [edit chassis] hierarchy level and then commit the configuration.

    1. [edit]

    2. user@host# set chassis realtime-ukern-thread

      user@host# commit

      The following warning message to reboot the system displays when you commit the configuration:

      WARNING: realtime-ukern-thread is enable. Please use the command request system reboot.

  2. Reboot the device to enable the configuration:

    1. user@host> request system reboot

  3. Verify that real-time BFD is enabled.

    user@host> show chassis realtime-ukern-thread

    realtime Ukern thread Status: Enabled

BFD Support By SRX Platform

SRX Series devices support the following maximum number of BFD sessions:

  • Up to four sessions on SRX100, SRX110, SRX210, SRX220, SRX300, and SRX320 devices.

  • Up to 50 sessions on SRX240, SRX340, SRX345, SRX380, SRX550, SRX550M, and SRX650 devices.

  • Up to 120 sessions on SRX1500 devices.

On all SRX Series devices, high CPU utilization triggered for reasons such as CPU intensive commands and SNMP walks causes the BFD protocol to flap while processing large BGP updates. (Platform support depends on the Junos OS release in your installation.)

SRX Series devices operating in chassis cluster mode support only BFD centralized mode.

The table below shows the BFD modes supported on each SRX Series device.

Table 1: BFD Modes Supported on SRX Series Devices

SRX Series Device

Centralized BFD Mode

Distributed BFD

Real-Time BFD

Dedicated Core

SRX100

Default

Configuration

Configuration (Optional)

Not supported

SRX110

Default

Configuration

Configuration (Optional)

Not supported

SRX210

Default

Configuration

Configuration (Optional)

Not supported

SRX220

Default

Configuration

Configuration (Optional)

Not supported

SRX240

Default

Configuration

Configuration

Configuration (Optional)

SRX300

Default

Configuration

Configuration (Optional)

Not supported

SRX320

Default

Configuration

Configuration (Optional)

Not supported

SRX340

Default

Configuration

Configuration

Configuration (Optional)

SRX345

Default

Configuration

Configuration

Configuration (Optional)

SRX380

Default

Configuration

Configuration

Configuration (Optional)

SRX550

Default

Configuration

Configuration

Configuration (Optional)

SRX550M

Default

Configuration

Configuration

Configuration (Optional)

SRX650

Default

Configuration

Configuration

Configuration (Optional)

SRX1500 BFD failure detection time > 500 ms and dedicated mode is not enabled BFD failure detection time < 500 ms and dedicated mode is not enabled Not supported Configuration
SRX4100 BFD failure detection time > 500 ms BFD failure detection time < 500 ms Not supported Not supported
SRX4200 BFD failure detection time > 500 ms BFD failure detection time < 500 ms Not supported Not supported
SRX4600 BFD failure detection time > 500 ms BFD failure detection time < 500 ms Not supported Not supported

SRX5400

Default

Not supported

Not supported

Not supported

SRX5600

Default

Not supported

Not supported

Not supported

SRX5800

Default

Not supported

Not supported

Not supported

SRX5000 line of devices with SPC3 card BFD failure detection time > 500 ms BFD failure detection time < 500 ms Not supported Not supported