Is it safe to open
SIP and VoIP ports are scanned constantly by toll-fraud bots looking for weak extensions. Allow only your provider's IP addresses on the firewall where possible, use long SIP passwords, fail2ban, and disable SIP ALG on the router.
How to open port 3478
Open to everyone
# Linux iptables iptables -A INPUT -p tcp --dport 3478 -j ACCEPT iptables -A INPUT -p udp --dport 3478 -j ACCEPT # Ubuntu ufw ufw allow 3478/tcp ufw allow 3478/udp # firewalld firewall-cmd --permanent --add-port=3478/tcp && firewall-cmd --reload firewall-cmd --permanent --add-port=3478/udp && firewall-cmd --reload # MikroTik /ip firewall filter add chain=input protocol=tcp dst-port=3478 action=accept place-before=0 comment="port 3478" /ip firewall filter add chain=input protocol=udp dst-port=3478 action=accept place-before=0 comment="port 3478" # Windows (PowerShell) New-NetFirewallRule -DisplayName "Port 3478 TCP" -Direction Inbound -Protocol TCP -LocalPort 3478 -Action Allow New-NetFirewallRule -DisplayName "Port 3478 UDP" -Direction Inbound -Protocol UDP -LocalPort 3478 -Action Allow
Only for your addresses
# allow only one address or network (replace 203.0.113.0/24) iptables -A INPUT -p tcp --dport 3478 -s 203.0.113.0/24 -j ACCEPT iptables -A INPUT -p udp --dport 3478 -s 203.0.113.0/24 -j ACCEPT iptables -A INPUT -p tcp --dport 3478 -j DROP iptables -A INPUT -p udp --dport 3478 -j DROP ufw allow from 203.0.113.0/24 to any port 3478 proto tcp ufw allow from 203.0.113.0/24 to any port 3478 proto udp /ip firewall filter add chain=input protocol=tcp dst-port=3478 src-address=203.0.113.0/24 action=accept /ip firewall filter add chain=input protocol=udp dst-port=3478 src-address=203.0.113.0/24 action=accept /ip firewall filter add chain=input protocol=tcp dst-port=3478 action=drop /ip firewall filter add chain=input protocol=udp dst-port=3478 action=drop
If the server is behind a router, you also need a port forward (dst-nat). Behind ISP CGNAT (100.64.0.0/10 on the WAN) forwarding will not help: you need a public IP or a VPN.
What is listening
Check on the server
# what listens on the port ss -lntup | grep ':3478 ' netstat -ano | findstr :3478 # Windows lsof -i :3478 # macOS # test from another machine nc -vz example.com 3478