FGT60E Android Devices Zoom / Office365 problems

[Rilas]

Hi everybody,

usually i try it myself as long as it solved but now i reached a point where i have no ideas, anymore.

Maybe someone of you can help me or have a idea what iam missing or doing wrong.

Here is my scenario:

- FortiGate 60E 6.2.3

- FortiGate 60E over VDSL 50 

- FortiGate has one Interface uplink with mutliple VLANs

Interface 1 (Network)

VLAN 100 DHCP active (Network 2)

VLAN 101 DHCP active (Network 3)

VLAN 102 (Network 4)

etc...

- FortiGate has one Interface uplink with an old network to supply the clients with the old Shares / DNS, which will be disabled soon

- to VLAN 100 two UniFi APs are Connected to provide W-Lan for clients

Everything works fine except two things:

Android Tablets with Office365 cannot sync E-Mails and the connection with zoom meetings.

What i have tried:

- Connect Windows Laptop over W-Lan to zoom = working

- Connect Windows Laptop over W-Lan to office365 = working

- Connect Windows Laptop over LAN to zoom = working

- Connect Windows Laptop over LAN to office365 = working

- Different Android Version Tablets connection Zoom over W-Lan = not working

- Same Tablets connection over LTE to Zoom = working

- Trying different Rulesets and ended with = VLAN 100 -> to any -> accept -> ALL -> no security -> no inspection Zoom / Office 365 still not working

- Updated Zoom APP = not working

- Controlled if UniFi APs have something enabled what they shouldnt have (like Packet-Inspection) -> nothing enabled

- Different other applications on the Tablets working normal and also playstore can update his apps

- Configured some FortiAP on a seperate Interface from the FortiGate to exclude Network Infrastructure issues or UniFi AP issues -> Connected Tablet to the AP -> Connected to zoom = not working

- Disable / remove MDM Software from Android Tablets and connecting Zoom over W-Lan = not working

We have different problems on the tablets

- One time audio worked, but no screen sharing and no video

- One time video worked, but no screen sharing and no audio

- Most time video not working, audio not working, screen sharing not working, but joining the meeting works

- Tablets get the information that screen sharing is active or video is active but black screen

- Same if i try to start video, screen sharing etc. on the tablets (the other getting information but nothing happens)

- Sometimes tablets do not even get to the point to join the meeting (connecting to meeting than hangs up - network issue)

- No E-Mail synchronisation with Office365

All Tablets are Samsung Galaxy

Summary:

Windows Laptops working normal in the same W-Lan

Tablets not working in the same W-Lan

And i already know, I´m just too stupid :)

[tanr]

Do the logs show anything from the tablets being blocked when users run into the problem from Android devices?

If you're using the ISDB for Zoom and Office365 on a policy without deep ssl inspection I would involve TAC. 

If their ISDB entry for these isn't working for Android devices they'll want to fix it.

[Dave_Hall]

This is purely speculation on my part with no actual research done, but in the back of my head, I'm thinking MTU on the Samsung Galaxy tablets needs to be adjusted. 

[Rilas]

Hi, thanks for the fast replies.

I changed the MTU Size on VLAN 7 for VDSL to 1400 (didnt helped), but I think that it could be the problem.

In the packet capture of the fortigate i see following

10.201.23.34 (Tablet) 34.240.76.216 (IP ZOOM) TCP 1514 [TCP Retransmission] 33501 → 443 [ACK] Seq=1 Ack=1 Win=197 Len=1448 TSval=4218040 TSecr=247354865

[This frame is  a (suspected) retransmission] 

And this i see a lot of times with different entries.

[Rilas]

Just for information.

Problem is solved.

One of the following three things fixed it.

- Update FortiGate from 6.2.3 to 6.2.4 

- Reboot of Firewall

- Zoom Update to 5.0