If you want to migrate from Skype for Business Server with telephony to Teams and Direct Routing the process might include the following steps: It is not enough to open for just one server since it is the server where the user is homed that opens the connection. They need to be able to authenticate and connect to the online services. This is because the Front-End servers log on SfBO when you move users online. You should also open for authentication services at ID 56 and 59 in the table. It is recommended to open all FQDN’s and IP address from the Front-End server to SfBO and as specified in the URLs and IP documentation for Teams and Skype. All Front-End servers with users need to have access to SfBO services.This is because the sip domain is shared between SfBO and SfBS. The Edge server needs to resolve its federation DNS records, it is therefore recommended to make sure you use a public DNS server on the public network leg on the Edge server.If you have configured federation in your environment today, then you have all components in place. The key element to a hybrid setup is that it is all federation traffic between your on-premises environment and Microsoft 365. Then you will get the best of both worlds, local telephony, familiar chat in SfBS and modern meetings in Teams. Skype for Business Server (SfBS) is still an optionīut you should set up hybrid and consider moving your meetings to Teams. Read my full article at Practical 365 on what the SfBO decommission means for you and how to get started with the move today:

Is skype for business going away