Can Browse the Web but Can’t Make Calls? Here’s Why (and How to Fix It)
Your internet works — your calls don’t. Here’s the actual reason
Websites load. The call drops immediately, or never connects at all. The instinct is to blame your ISP or your Wi-Fi signal, but neither is usually the problem. The real issue comes down to one word: protocol.
Web browsing runs on TCP. Calls run on UDP. Your router may be handling them very differently, and that gap is where things break.
TCP vs UDP — why it matters for calls
TCP is the reliable one. If a packet gets lost, TCP resends it. That’s fine for loading a webpage — a few extra milliseconds to retry doesn’t matter. Voice and video calls can’t wait. They use UDP, which fires packets and doesn’t look back. Faster, but your router needs to handle UDP flows correctly or they vanish.
Many home routers time out UDP connections aggressively, or block them outright under certain firewall settings. The TCP traffic that carries your browser sessions passes through just fine. The UDP traffic your calling app needs gets dropped quietly.
SIP ALG: disable this first
SIP ALG stands for Application Layer Gateway. It was designed to help VoIP calls get through NAT. In practice, it tends to corrupt the SIP signaling packets that set up calls — rewriting them in ways the receiving server doesn’t understand. The call never establishes. Or you hear nothing.
It’s enabled by default on a lot of consumer routers. Turn it off before you do anything else.
Log into your router admin panel — typically at 192.168.1.1 or 192.168.0.1 in a browser. Look for a setting called SIP ALG, VoIP ALG, or VoIP Helper. Disable it, save, reboot the router, then try a call. This alone fixes the problem more often than you’d expect.
Blocked UDP ports
VoIP signaling typically uses UDP port 5060 (or 5061 for encrypted traffic). The actual audio stream travels over a range of RTP ports, commonly UDP 10000–20000, though this varies by app and provider. If your router’s firewall has broad rules blocking outbound UDP, those ports get caught in the net.
- SIP signaling: UDP 5060 (plain) or 5061 (TLS)
- RTP audio: UDP 10000–20000 is a common range — check your specific app’s documentation for exact ports
- Apps like Zoom, WhatsApp, or Teams use UDP on their own port ranges; each publishes its network requirements
You don’t necessarily need to set up port forwarding. But if your firewall is actively blocking outbound UDP, a rule to permit it will help.
Is the ISP blocking VoIP?
Some ISPs — particularly in markets where traditional carriers still hold influence — throttle or block VoIP traffic at the network level. This is separate from anything happening on your router.
A quick test: switch off Wi-Fi and try the same call over mobile data. If it works there but not on your home network, and disabling SIP ALG didn’t fix it, your ISP may be filtering VoIP. A VPN tunnel will usually bypass this, since the call traffic looks like encrypted data to the ISP rather than identifiable VoIP packets.
QoS and bandwidth contention
Even if calls connect, they can break up or cut out if your router is saturating the upload link with something else. Calls need consistent low latency, not just raw bandwidth. Quality of Service lets you prioritize voice traffic so it jumps the queue. Look for QoS in your router settings and mark UDP voice traffic as high priority. This won’t fix a hard block, but it helps on congested connections.
Quick checklist
- Disable SIP ALG in your router admin panel and reboot
- Test the same call over mobile data to check whether the problem is the router or the ISP
- Try a different calling app — if one works and another doesn’t, the block is app-specific
- Review router firewall rules for anything blocking outbound UDP broadly
- On corporate, hotel, or school Wi-Fi: UDP is commonly restricted by policy and a VPN is usually the only way around it
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