Description

This article explains how to determine the session rate on Juniper SRX devices and provides commands to monitor session usage, session creation rate, and PFE-level session statistics.

Symptoms

The following symptoms may indicate high session rate or session resource utilization:

  • High session rate
  • High PFE CPU utilization
  • Packet drops
  • Firewall reaching the session limit
  • Performance degradation

Solution

1. Check Current Session Usage

First, obtain an overview of the current session usage by checking the session statistics.

Use the following command:

show security flow session

This command displays the current active sessions and provides the total number of active sessions on the device.

To view a summarized session overview, use:

show security flow session summary

This command provides high-level session statistics, including:

  • Total active sessions
  • Sessions in use
  • Failed sessions
  • Invalidated sessions
  • Other session-related counters

2. Check Session Statistics at the PFE Level

To check session information from the Packet Forwarding Engine (PFE) level, use:

(vty)# show usp flow session summary

This provides session statistics directly from the forwarding plane.

3. Monitor Session Rate

To monitor the session creation rate, use:

show security monitoring performance session

Run this command multiple times at different intervals to determine:

  • Current session rate
  • Whether the session rate is constant or irregular
  • Changes in session creation activity over time

A continuously increasing session rate may indicate abnormal traffic patterns or resource exhaustion.

4. Check Session Details at the PFE Level

The command to check detailed session information depends on the SRX platform.

Branch SRX Series (SRX3xx and SRX550M)

(vty)# show octeon session detail

Data Center SRX Series (SRX1500, SRX4k), SPC3, and vSRX

(vty)# show i386 session detail

High-End SRX Series (SRX1k, SRX3k, and SRX5k)

(vty)# show xlr session detail

5. Check Session Creation Rate and PFE Resource Utilization

Use the following command:

show security monitoring fpc 0

This command displays:

  • PFE CPU utilization
  • Memory utilization
  • Current session rate
  • Session creation rate (sessions created per second)

This information helps identify whether the SRX device is approaching resource limits or experiencing abnormal session creation activity.

Modification History

v1