Cisco Webex Audio not working

Question

Good day folks, 
 I have an issue where Cisco webex does not play any audio when connecting via their computer. Everything else works. I have been trying to figure this out for a day and I'm getting nowhere it seems so I'm reaching out for some help. I have an XG230 firewall running 17.5.10 MR-10. These are the associated errors I can see:

2020-04-10 14:10:07

Invalid Traffic

Denied

0

x.x.x.x

209.197.193.92

63495

443

TCP

0

01001

Open PCAP

Invalid TCP RST.

020-04-10 14:00:14

Invalid Traffic

Denied

0

x.x.x.x

209.197.193.92

62971

443

TCP

0

01001

Open PCAP

Invalid TCP RST.

2020-04-10 14:00:11

Invalid Traffic

Denied

0

x.x.x.x

209.197.193.92

62967

443

TCP

0

01001

Open PCAP

Invalid TCP RST.

I do have an HTTPS exception for Webex but all I have in there is..the 1 more is .webex.com 
 
 Any thoughts on where I can look to straighten this out? I have tried googling for hours and keep coming up with dead ends. Thanks! 
 
 Scott

Dom Nik · Accepted Answer

Hi together, 
 we debugged it together with Sophos in a live session and finally got a working solution. :-) (NC-59268) 
 These are my settings and it's working like a charm: 
 - https scanning using IPS is fully active, no exceptions for Webex. 
 - Ports in addition to 443/https: 
 
 - The following setting does the trick as of v18 MR1 (there was a change with MR1 making the setting necessary - it seems to be implicitly active in previous releases): 
 set http_proxy relay_invalid_http_traffic on 
 - No more configuration or https-scan exceptions needed and audio/video seems to work through UDP ports with better performance/latency than fallback solutions using 443/tcp. 
 Hope this helps! 
 Thanks to Rana Sharma , -pete- , Elardus, Apurv Patel , deepti.bhavsar and Tim. (hope I did not forget someone). 
 Best Regards 
 Dom

Dom Nik · Answer

Hi together, 
 I tested it with v18 MR1 and got it to work with with 443/tcp and 9000/udp open, using DPI instead of Web Proxy and ATP completely switched off. (It is not sufficient to add a exception in ATP. It really needs to be off. Afterwards the appliance needs a reboot.) 
 Best Regards 
 Dom