The following are the requirements of Skype for Business Online for Office 365, note this information can change as the service evolves. This is from the clients machine to Office 365
Firewall Ports
Port Destination | Protocol | Client Usage | Direction |
443 |
TCP |
SIP Signalling |
Outbound |
443 |
TCP |
Audio, Video, Application sharing sessions and Web Conferencing |
Outbound |
3478 |
UDP |
Audio and Video Sessions |
Outbound |
5223 |
TCP |
SfB Mobile push notifications – iOS Only |
Outbound |
50000 TO 59999 INCLUSIVE |
RTC/UDP/TCP |
Audio and Video Sessions |
Outbound |
50000 TO 59999 INCLUSIVE |
TCP |
Application Sharing and File Transfer |
Outbound |
The following is the URL’s that SfB Online from the client will use to get to the SfB Online servers so if the traffic is going through internet proxies and you are having issues these URL’s will be helpful:
*.lync.com
crl.microsoft.com
evsecure-ocsp.verisign.com
evsecure-aia.verisign.com
evsecure-crl.verisign.com
sa.symcb.com
sd.symcb.com
*.omniroot.com
*.verisign.com
*.symcb.com
*.symcd.com
*.verisign.net
*.geotrust.com
*.entrust.net
*.public-trust.com
Finally the last point is if your firewall guys want to lock down access to specific IP addresses (although NOT recommended due to the fact these can be changed) Please refer here: