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salassilvaj
Explorer III
July 14, 2026
Question

vpn ssl subinterface stop working but internet is reachable

  • July 14, 2026
  • 9 replies
  • 96 views

vpn ssl stop working but internet is reachable,

my topology is a sdwan connection to internet from two wan sub interfaces joined as sdwan members into a sdwan-zone, we are using the fortigate lower models and firmware are 7.4.0 and 7.2.4, internet connection are asymmetric, home-residential massive internet. SLA health check is active but ramdonly after a couple of days internet connection is up but vpn ssl sub interface is down, no echo-ping goes back and sniffer also doesn´t show anything, only remote solution is to reset port and after that sub interface goes up again. Following current sdwan config

    edit 3
        set interface "subinterface-primary-vpn"
        set zone "sdwan-to-remote-hub"
    next
    edit 4
        set interface "subinterface-backup-vpn"
        set zone "sdwan-to-remote-hub"
    next

...
 edit "vpn-health-check"
        set server <remote-looback-ip>
        set interval 1000
        set failtime 10
        set recoverytime 10
        set source <local-lan-ip-allowed>
        set members <sub interfaces members 3 4>
next


config service
    edit 3
        set name "primary-internet-to-hub-concentrator"
        set mode priority
        set dst "all"
        set src "all"
        set health-check “vpn-health-check"
        set priority-members 3
    next
    edit 4
        set name "back-internet-to-hub-concentrator”
        set mode priority
        set dst "all"
        set src "all"
        set health-check “vpn-health-check"
        set priority-members 4
    next

….

Also consider a static default route pointing to this sdwan-zone so, that way server <remote-looback-ip> is reachable throughtout this zon

Greetings

9 replies

sjoshi
Staff
Staff
July 15, 2026

@salassilvaj  what do you mean by vpn ssl sub interface? Are you talking about ssl vpn? or do you mean member 3 and 4 sla is down in sdwan health check?

can you elaborate more on the issue

Thanks, Salon
salassilvaj
Explorer III
July 15, 2026

i mean, vpn ssl depending on physical interface, vpn ssl health check is down only for this internet connection (primary) but internet is up, device is reachable from a secondary backup connection so that way we can reach the device from it and identify this issue and troubleshoot

sjoshi
Staff
Staff
July 15, 2026

you mean ssl vpn connection on pri interface was down and sla health check on pri interface was down but internet was still working on pri interface?

Thanks, Salon
henry-collins
Visitor III
July 17, 2026

It is an SD-WAN policy issue and more like the VPN interface or underlying session getting stuck. Since internet traffic keeps working but the SSL VPN subinterface stops responding until you reset the port, check for known bugs in those firmware versions first and review the logs around the time it happens. If possible, try upgrading to a newer patch release, as 7.2.4 and 7.4.0 have had fixes for VPN-related stability issues. Also, opening a TAC case with debug logs captured before resetting the port would likely speed up finding the root cause.

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salassilvaj
Explorer III
August 2, 2026

following ike debug found
2026-08-02 hh:mm:ss primary-connection-tunel-1: using existing connection
2026-08-02 hh:mm:ss primary-connection-tunel-1: traffic triggered, serial=1 1:<loopback-ip>:2048->1:<remote-hub-ip>:0
2026-08-02 hh:mm:ss primary-connection-tunel-1: config found
2026-08-02 hh:mm:ss primary-connection-tunel-1: request is on the queue

following phas1-interface vpn config shows also net-device enable and phase2-interface vpn config, also phase-1 is still state connecting even after upgrade from 7.4.0 to 7.4.1


edit "primary-connection-tunel-1"
        set interface "wan"
        set ike-version 2
        set peertype any
        set net-device enable
        set proposal aes128-sha256
        set add-route disable
        set localid "my-local-id"
        set npu-offload disable
        set auto-discovery-receiver enable
        set network-overlay enable
next
...
config vpn ipsec phase2-interface
    edit "primary-connection-tunel-1"
        set phase1name "primary-connection-tunel-1"
        set proposal aes128-sha1
        set auto-negotiate enable
    next

...

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