Forum Discussion

KennethML's avatar
KennethML
MCT
Mar 28, 2017

Unknown Office 365 IP address

I saw at a customer site today, a STUN request going from the client to 13.100.4.192. By looking at the src and dest ports, I would say this is a video session trying to establish a connection to a m...
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Kevin Van Hee's avatar
Kevin Van Hee
Copper Contributor
Dec 04, 2018

We noticed the same phenomenon. We had a lot of users reporting issues when having Skype for Business calls with external participants or when having a call with multiple participants. Both scenario's connect to SfB online. 

Internal point to point call did not show any issues.

 

This pointed us in the direction of the firewall in place between our network and the Microsoft (SfB) cloud environment.

 

After extensively going through the firewall logs and cross linking with the call quality dashboard now available on the Teams & Skype for Business admin portal we noticed a lot of drops by the firewall.

 

When investigating these drops we noticed a lot of inconsistencies with the documentation provided by Microsoft.

  • High ports range 50000-59999 should actually be 49152-65535
  • Connections towards 13.100.x.x ranges (UDP3478-3481) -> After WhoIs lookup the subnet is actually 13.96.0.0/13

This inconsistencies caused a lot of performance issues and users complaining about calls being dropped, content sharing issues, etc...

  • rameshram18's avatar
    rameshram18
    Copper Contributor
    Dec 04, 2018

    The 13.100 series are only the Host IPs. Not necessarily it needs to be route-able publicly.  It would by default try connecting direct and fail. We need to worry only about Relay IP which is 52.112 on most cases. 

     

    a=candidate:1 1 tcp-pass 2120613887 13.100.10.217 61560 typ host
    a=candidate:2 1 tcp-act 2121006591 13.100.10.217 62483 typ host
    a=candidate:3 1 tcp-pass 174455807 52.112.0.193 59614 typ relay raddr 13.100.10.217 rport 61049
    a=candidate:4 1 tcp-act 174848511 52.112.0.193 59614 typ relay raddr 13.100.10.217 rport 61049