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5.6.0 breaks deep packet inspection

Going to open a ticket on this as well but wanted to see if anyone else had this same issue. Did the upgrade from 5.4.3 to 5.6.0 and as far as I can tell nothing changed in our policies except the deep packet inspection profile was automatically renamed from 'deep-inspection' to '__upg_deep-inspection' for some reason. Applications like Skype and Outlook are no longer connecting even though exceptions are in the list and it worked before the upgrade. Also going to certain websites will display a 'webpage is not available' error quickly before refreshing and finally going to the site.

New Contributor III

We are having an issue where previously logged applications signatures like "Microsoft.Portal", "OneDrive", "Facebook" etc are no longer being logged after upgrading from 5.4.9 to 5.6.10.  These signatures are now being reported/logged as "unknown" applications.  Does not seem to be an issue on 5.6.8 or 5.6.9 however.  We want to stay on 5.6.10 to mitigate multiple CVEs bug the application logging is concerning.


Anyone else notices this on 5.6.10?

New Contributor III

FYI, I recently updated from FortiOS 5.6.11 to FortiOS 6.0.6 and have not encountered the issue anymore. All HTTPS websites load properly now. DPI seems to work well on FortiOS 6.0.6.

New Contributor III

FYI, it seems the problem started again on FortiOS 6.0.9. Websites sometimes do not load on first attempt and are only displayed after a refresh, so exactly the problem we had pre FortiOS 5.6.11. I am seeing this on FortiGates 201E, 301E and 51E. Everything was still fine on FortiOS 6.0.8 and all the other versions of the 6.0.x branch actually. Problem only started again with FortiOS 6.0.9.


Is anyone else seeing this?

New Contributor III

Don't upgrade to 6.2.3, deep inspection is totally broken for me. Im using Transparent proxy. I was on version 6.0.8 and it had no issues . 

New Contributor III

We are now on FortiOS 6.0.10 and are still experiencing this problem. There are intermittent delays when HTTPS websites are opened. We see this in all browsers. In e.g. Google Chrome we see "Waiting for" in the bottom left corner. Sometimes it takes 10-15 seconds before anything appears at all.


Quite difficult to reproduce this but I have excluded a few common HTTPS websites from DPI (added these domains to the SSL exemption list) and the problem went away for those websites - so this definitely points to SSL/Deep Packet Inspection. We use proxy-based inspection (cannot switch to flow-based inspection due to certain security profiles that only work in proxy-mode). On the IPv4 policy we also enable Web Filter, AntiVirus and Intrusion Prevention security profiles.


If anyone has any ideas how to resolve this, please let me know. I have not updated to FortiOS 6.0.11 yet but I doubt this will fix anything as this has been broken for a while. I have also been thinking about updating to FortiOS 6.2.5. Does anyone have any information whether or not this is working better on FortiOS 6.2.5?

New Contributor III

FYI, just in case anyone else is experiencing this:

The problem was caused by packet loss between FortiGate and FortiGuard. In "System - FortiGuard" we changed the "FortiGuard Filtering Protocol" from HTTPS to UDP. Using HTTPS we experienced high packet loss in almost all branches (run diagnose debug rating). Using UDP there is hardly any packet loss. The performance difference between HTTPS and UDP is incredible. Websites load instantly now. However, we would obviously like to use HTTPS, so we are still investigating.

Valued Contributor

have you looked in using anycast instead or regular HTTPS?


so far that seems to work better, but still not so well as UDP.

New Contributor III

We are still on FortiOS 6.0.10 and anycast is not supported on this build as far as I know. Pity.


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