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[J/SRX] How to troubleshoot a VPN tunnel that is going up and down

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Article ID: KB10096 KB Last Updated: 18 Jun 2015Version: 8.0
Summary:

This article will help you determine the reason why your VPN tunnel between two VPN devices is going up and down.  Follow the steps until the problem is resolved or a case needs to be opened with your technical support representative.

This article is part of the troubleshooting guide: KB10100 - Resolution Guide - How to troubleshoot a VPN tunnel that is down or not active.


Symptoms:

I have a site-to-site VPN tunnel or a Remote IPsec VPN that is going up and down.  How do I troubleshoot it?


Cause:

Solution:

Use the following steps to assist with resolving a VPN tunnel that is going up and down.

Note: If your VPN is down, then go to KB10100 - Resolution Guide - How to troubleshoot a VPN tunnel that is down or not active. If your VPN is going up and down, then proceed with the following steps.

Step 1. Does the issue affect one VPN or all configured VPNs?


Step 2.  Are there system logs reporting that the VPN is flapping or unstable?

Run operational command:  > show log messages

Note: Info level logging is necessary for proper message reporting.  Use the command:           # set system syslog file messages any info

Below are examples of system logs showing a VPN tunnel reporting up and down:

VPN UP/DOWN events:

Jul 9 21:07:58 kmd[1496]: KMD_VPN_DOWN_ALARM_USER: VPN to_hub from 3.3.3.2 is down. Local-ip: 4.4.4.4, gateway name: to_hub, vpn name: to_hub, tunnel-id: 131073, local tunnel-if: st0.0, remote tunnel-ip: 70.70.70.1, Local IKE-ID: 4.4.4.4, Remote IKE-ID: 3.3.3.2, XAUTH username: Not-Applicable, VR id: 4
Jul 9 21:08:10 kmd[1496]: KMD_VPN_UP_ALARM_USER: VPN to_hub from 3.3.3.2 is up. Local-ip: 4.4.4.4, gateway name: to_hub, vpn name: to_hub, tunnel-id: 131073, local tunnel-if: st0.0, remote tunnel-ip: 70.70.70.1, Local IKE-ID: 4.4.4.4, Remote IKE-ID: 3.3.3.2, XAUTH username: Not-Applicable, VR id: 4
Jul 9 21:09:58 kmd[1496]: KMD_VPN_DOWN_ALARM_USER: VPN to_hub from 3.3.3.2 is down. Local-ip: 4.4.4.4, gateway name: to_hub, vpn name: to_hub, tunnel-id: 131073, local tunnel-if: st0.0, remote tunnel-ip: 70.70.70.1, Local IKE-ID: 4.4.4.4, Remote IKE-ID: 3.3.3.2, XAUTH username: Not-Applicable, VR id: 4
Jul 9 21:10:10 kmd[1496]: KMD_VPN_UP_ALARM_USER: VPN to_hub from 3.3.3.2 is up. Local-ip: 4.4.4.4, gateway name: to_hub, vpn name: to_hub, tunnel-id: 131073, local tunnel-if: st0.0, remote tunnel-ip: 70.70.70.1, Local IKE-ID: 4.4.4.4, Remote IKE-ID: 3.3.3.2, XAUTH username: Not-Applicable, VR id: 4

Unstable VPN Behavior (VPN constantly rebuilding)

Jul 9 20:43:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: inbound, SPI: 0xfd91b643, AUX-SPI: 0, Mode: Tunnel, Type: dynamic
Jul 9 20:43:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: outbound, SPI: 0xbdec9669, AUX-SPI: 0, Mode: Tunnel, Type: dynamic
Jul 9 20:44:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: inbound, SPI: 0x69b34ae4, AUX-SPI: 0, Mode: Tunnel, Type: dynamic
Jul 9 20:44:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: outbound, SPI: 0x6f55d8ea, AUX-SPI: 0, Mode: Tunnel, Type: dynamic
Jul 9 20:45:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: inbound, SPI: 0x6fa6b0b3, AUX-SPI: 0, Mode: Tunnel, Type: dynamic
Jul 9 20:45:10 kmd[1496]: KMD_PM_SA_ESTABLISHED: Local gateway: 4.4.4.4, Remote gateway: 3.3.3.2, Local ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Remote ID: ipv4_subnet(any:0,[0..7]=0.0.0.0/0), Direction: outbound, SPI: 0xa66ac906, AUX-SPI: 0, Mode: Tunnel, Type: dynamic


  • Yes - Continue with Step 3.
  • No  - However VPN is going UP/Down, jump to Step 6



Step 3.  Is VPN Monitor enabled for this VPN?  For assistance, consult KB10118 - How do you enable the Optimized feature of VPN Monitor and what does it do?.

  • Yes - Continue with Step 4.
  • No   - Jump to Step 6.


Step 4.  Temporarily disable VPN Monitor.  Is the VPN stable?

    Run the commands:
    # deactivate security ipsec vpn <vpn_name> vpn-monitor
    # commit
  • Yes - The instability is related to the VPN Monitor configuration.  Continue with Step 5.
  • No   - Jump to Step 6.

Step 5.  Is the remote VPN connection configured to block ICMP Echo Requests?



Step 6.  Is the remote VPN connection a non-Juniper device?  



Step 7.  Was the VPN stable for a period of time and now it is going up and down?

  • Yes - Investigate for network or device changes or if any new network equipment has been added to the environment. If so, confirm changes/additions are correct.
  • No   - Continue with Step 8.


Step 8. Collect site-to-site logs from the VPN devices at both ends and open a case with your technical support representative.

Consult: KB21781 - [SRX] Data Collection Checklist. See the IPsec VPN Policy-based or Route-based sections.


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