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[SRX] How to troubleshoot a site-to-site VPN where the SA is Up but the Monitor status is Down on the device

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Article ID: KB10104 KB Last Updated: 26 Mar 2020Version: 10.0
Summary:

This article describes how to troubleshoot a site-to-site VPN where the SA is Up but the Monitor status is Down on an SRX Series device.

Symptoms:

Symptoms and Errors

  • Traffic is not passing through the tunnel.
  • The tunnel's SA is UP, but the Monitor status is Down.
> show security ipsec security-associations
Total active tunnels: 1
ID Algorithm SPI Life:sec/kb Mon lsys Port Gateway
<268173356 ESP:aes-cbc-128/sha1 5895f48b 2086/ unlim D root 54017 10.10.10.10
>268173356 ESP:aes-cbc-128/sha1 16693188 2086/ unlim D root 54017 10.10.10.10
Solution:

Perform the procedure below to troubleshoot a VPN Tunnel in which the SA is Active but the Monitor status is Down. (To view a flowchart of the procedure, see KB10104.)

Step 1.  Is this a Site-to-Site (or LAN-to-LAN) VPN?  (A Site-to-Site VPN runs between two Juniper VPN devices or a Juniper VPN device and an OEM VPN device. A Site-to-Site VPN does not run between the Juniper VPN device and a PC client running VPN software.)

Step 2.  Is the IKE SA (Security Association) UP? Is the Mon Status DOWN?  (For assistance, see KB10090 - How do I tell if a VPN Tunnel SA (Security Association) is active on a J Series or SRX Series device?.)

Step 3.  Is the VPN Monitor "Optimized" feature enabled for this VPN?  (For assistance, see KB10118 - How do you enable the optimized feature of VPN Monitor on a J Series or SRX Series device, and what does it do?)

  • Yes - Proceed to Step 4.
  • No  - Enable the VPN Monitor "Optimize" setting and test the VPN connection again.  
Step 4  Temporarily disable the VPN Monitor (to further troubleshoot the issue).
  • From J-Web: Go to Configure > IPSec VPN >Auto Tunnel > Phase II >Auto Key VPN and uncheck the Enable VPN monitor box. 
  • From CLI: Enter this command: deactivate security ipsec vpn <vpn_name> vpn-monitor.

Step 5  With the VPN Monitor disabled, is the policy passing data? (For assistance with enabling logging, consult: KB10112 - Configuring the Junos Traffic Log.

Step 6.  Is the remote VPN connection a non-Juniper VPN Firewall device, or is the remote VPN device configured to block ICMP Echo Requests?

Step 7  Collect logs and open a case with JTAC (Juniper Technical Assistance Center). (For assistance, see KB21781 - [SRX] Data Collection Checklist - Logs/data to collect for troubleshooting.)

Modification History:
2020-03-26: Article reviewed for accuracy; it is valid and accurate

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