SignalWire does not publish a list of IPs for public consumption as IPs may change. Customers can periodically run a command, or create a service to update firewalls regularly: dig sip.signalwire.com | egrep ^sip | awk { print $5 } | xargs -n1 -I{} iptables -A INPUT -s {} -j ACCEPT dig relay.signalwire.com | egrep ^relay | awk { print $5 } | xargs -n1 -I{} iptables -A INPUT -s {} -j ACCEPT dig firewall.signalwire.com | egrep ^firewall | awk { print $5 } | xargs -n1 -I{} iptables -A INPUT -s {} -j ACCEPT It is highly recommended to use domain-based authorizing as those are subject to change! Media comes from a wide variety of locations and is non-deterministic.