Recently I have upgraded two clients to the newest firmware released for Fortigates, 5.0.5. Both clients heavily utilize iOS in their environments and somewhere along the upgrade path to 5.0.5, iOS traffic seems be down right blocked or they start downloads but the downloads are never successful. By blocked, the user will attempt to download iOS updates, iBooks, applications, etc and either the download never starts and eventually times out or the download does start but only gets a few Mb in before it stops. One client has even reported this extends to Mac users attempting to use iTunes.
Besides the firmware upgrade to 5.0.5, nothing about these clients networks have changed. Each are using different wireless setups, different switching, etc. One client has a Fortigate 100D and the other 2x300C in an Active-Active HA cluster.
During testing with each client, I have disabled everything down to the web filter. With the web filter active, the problems exists but with the web filter disabled, users can download successfully. The traffic and web filter UTM logs show no traffic being blocked. In testing, the web filter was set to allow all and web filter exceptions were placed for common URL's seen in traffic logs while users browsed to Apple/iOS related applications.
I have attempted to work with Fortinet support on the issue but their solution has been to factory reset each firewall, re-import the config, and follow the firmware upgrade matrix again in case there was corruption in the previous upgrade. They have no been able to indicate that there actually are any signs of corruption and the 300C client firewalls came out of the box only one build behind the most recent release, so I highly doubt there was corruption upgrading one firmware release.
At this point I am contemplating downgrading the firmware on each firewall until I find the most recent release that this problem does not exist but the point of upgrading in the first place was to fix other bugs in the ipsengine and proxyworker processes that were causing issues.
Thanks for any help.