The article provides developer guidance for connecting to Vivox servers through firewalls, specifying destination IP ranges and TCP/UDP ports.
FQDN List
Vivox does not publish a fixed per-project FQDN allowlist, and we do not recommend allowlisting by FQDN alone. The backend has multiple components whose IPs can change, and the UDP voice media does not route through named hosts, so FQDN rules cannot cover it.
IP Subnets
The following list is current as of July 28, 2026.
85.236.96.0/21 85.236.104.0/23
Note: A single environment has multiple backend components that could change IPs without warning.
Port Ranges
All communications start as outbound communications from the client and only require that a firewall allows communication back on the same UDP port.
- TCP: 443 - for web server (HTTPS)
- UDP: 12000 - 52000 - for voice media (RTP)
SSL/TLS Inspection
This can cause firewall-related failures with Vivox. The control channel uses standard HTTPS on TCP 443. Proxies or firewalls that perform SSL/TLS inspection can cause connection or certificate errors (for example status code 10077, HTTP Invalid Certificate). SSL/TLS inspection should be disabled or excepted for *.vivox.com so the control traffic is not modified. The UDP media (12000 to 52000) does not pass through an HTTP proxy and must be allowed to egress directly.