On the 23rd April 2019, Nexmo will be expanding the port range used for RTP/media for all Voice traffic, to use all ports available. We also wish to announce the IP ranges that Nexmo will use for all RTP traffic, which you will need to whitelist on your firewall.
Port range - All
IP ranges - 184.108.40.206/28, 220.127.116.11/27, 18.104.22.168/28, 22.214.171.124/28, 126.96.36.199/28
We recommend that you whitelist all IP ranges and allow all ports immediately to avoid any disruption. After 23rd April 2019, you may experience silent calls if the above IP ranges and ports have not been allowed. Please note that these changes will be happening to all data centers in the Nexmo platform.
We apologize in advance for any inconvenience this may cause. If you have any questions, please don’t hesitate to reply to this email or submit a support request at https://help.nexmo.com