Published on: 2018-10-08

In our company we recently enabled IPv6 in Dual-Stack mode (which means we have a ipv4 and a ipv6 address). We have noticed nearly no failures but since we enabled ipv6 for the client network Skype for business isn´t able to login anymore. We found out a workaround to disable ipv6, login and enable it again which will also work but it isn´t satisfactory for us.

I found then some threads about MTU problem from sfb and tried this on my pc on this also works.

On Windows 10 it is possible to change the MTU of a single interface only for ipv6 or ipv4, so i changed the ipv6 mtu from 1500 (which is standard) to 1480 with which sfb will work.

Netsh interface ipv6 show interfaces

to detect which is the currently active interface

Netsh interface ipv6 set subinterface “7” mtu=1480 store=persistent

to set the MTU of the interface to 1480.

This is also not a nice workaround but needs to done done only a single time and not every day. Hopefully Microsoft will fix this someday…

Sources:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_sfb-mso_mac-mso_o365b/skype-for-businesslync-services-dont-appear-to/c204b511-8b0b-4338-924e-729603627413/
https://www.skypefeedback.com/forums/299913-generally-available/suggestions/33748453-fix-the-badly-broken-ipv6-stack/

https://krausens-online.de/windows-10-setzen-der-mtu-aller-netzwerkkarten-ausser-loopback/