Forum Discussion
Network connectivity test TCP Connection results unreliable
My team has spent the last 2 business days trying to get the https://connectivity.office.com/ TCP connection test to complete successfully to appease the Microsoft Unified Support Team. They don't want to take our MS Teams crash diags until they see SSL Interception Detection and TCP connection tests passing successfully.
We can't get TCP connection tests to pass, we get one of the following:
- Success
- Attempt #1 Success, Attempt #2 Failure
- Any number of errors to unblock URLs such as (but not limited to) ocsp.digicert.com,ocspx.digicert.com,ocsp.omniroot.com,su.symcb.com,sr.symcb.com,sd.symcb.com,s1.symcb.com,sa.symcb.com
We figured it was something with the corporate network but that's not the case. Last night we had about 50 employees try this test from their home (personal) computers that have no connection to our corporation.
The TCP Connection test fails on home (consumer) PCs.
What's the story with this TCP Connection check?
1 Reply
Consider this:
- Whitelist Microsoft 365 Endpoints
Ensure your firewall, proxy, or endpoint security software allows traffic to all Microsoft 365 URLs and IPs.
- Disable SSL/TLS Inspection
If you’re using any kind of SSL inspection (even at home via antivirus), disable it for Microsoft endpoints. These include:
- *.microsoft.com
- *.office365.com
- *.digicert.com
- *.symcb.com
- Use a Clean Test Environment
Try running the test from a clean Windows install with no antivirus, VPN, or proxy settings. Use a wired connection if possible.
- Check DNS Resolution
Use a reliable DNS provider like Google (8.8.8.8) or Cloudflare (1.1.1.1) to ensure proper resolution of OCSP endpoints.
- Run the Test Authenticated
Sign in to the test site with your Microsoft 365 account. This can improve accuracy and provide tenant-specific diagnostics.
