Ringcentral not making calls

TLDR: Reduce the MTU on your laptop to enable Ringcentral to make calls.

The other day I was testing RingCentral on my laptop to replace desktop phones.  The mobile app worked perfectly, but the desktop app would not make outbound calls.  They were “connecting” but never rang the remote phone.

A few PCAPs later and I noticed the router was sending ICMP messages about not being able to fragment the packets being sent.  Reducing the MTU to eliminate the fragmenting problem, and everything worked as expected.

The windows commands that were run are:

netsh interface ipv4 show subinterface
netsh interface ipv4 set subinterface interface=Ethernet mtu=1400 store=persistent

I hope this helps.

-Adam

Hello World

Hello World!

This is a blog for me to write thoughts about computers, computer security, system integration, system testing, and other things.  I’m glad you’ve stopped by!  Hopefully you find some notes I make useful.