What Is Starlink’s CGNAT Limitation?
Starlink’s CGNAT limitation is a technical restriction where Residential and Roam users share IPv4 addresses through carrier-grade network address translation, with each account capped at 1,200 simultaneous TCP or UDP sessions, so opening more connections forces older ones to be dropped and can disrupt activities that depend on stable, ongoing internet communication. In plain terms, every app, tab, call, or game you run opens multiple “sessions” to remote servers. Starlink’s system counts these and, once you hit 1,200 at the same time, new connections push old ones off the list. The company notes this can interrupt VoIP calls, video meetings, online games, and VPNs without warning. Understanding that there is a hard ceiling on concurrent sessions helps explain sudden call drops or game disconnects even when your speed test looks fine.
Why Starlink Uses Carrier-Grade NAT
Carrier-grade NAT (CGNAT) exists to stretch a limited pool of IPv4 addresses across many customers. Instead of giving every Starlink user a unique public IPv4 address, Starlink places subscribers behind shared addresses and tracks who is who with internal session tables. According to PCMag’s reporting on Starlink’s support pages, CGNAT is a common technique and is “required to scale limited v4 address space resource to millions of customers on large ISP networks,” as networking consultant Daryll Swer explains. Starlink does support IPv6, which reduces pressure on IPv4, but many websites and services still only speak IPv4. GitHub and various legacy sites fall into this group, so CGNAT remains necessary. The 1,200 concurrent-session cap is Starlink’s way of keeping any one user from monopolising shared IPv4 resources, which is a standard practice for CGNAT deployments.
How Internet Session Limits Affect Real-World Use
Most households never notice the Starlink CGNAT limitation, because many popular services run over IPv6 and do not count against the IPv4 session table. Daryll Swer estimates that around 80% of an average Starlink customer’s traffic could go over IPv6 via platforms like Cloudflare, Amazon Web Services, and Google Cloud, leaving about 20% on IPv4. Still, internet session limits can show up during heavy use. Each video call, online game, or VPN tunnel opens multiple concurrent connections, and many browser tabs or cloud apps can add dozens more. When the 1,200-session cap is reached, Starlink says “new sessions automatically cause the oldest sessions to be dropped,” which may look like random call drops, stuck file uploads, or game disconnects. The more devices and always-online apps you have, the easier it becomes to hit this threshold during busy periods.
Spotting Symptoms of Starlink’s CGNAT Issues
Because the Starlink CGNAT limit targets simultaneous IPv4 sessions, its symptoms differ from slow-speed or weak Wi-Fi problems. Speed tests can appear normal while real-time apps misbehave. Typical signs include VoIP or video calls that cut out after several minutes, online games that disconnect even when latency looks acceptable, VPN tunnels dropping unexpectedly, and web pages that occasionally refuse to load until you refresh. These issues often appear when many devices are active together and fall away when usage calms down. Session drops can also be bursty: opening a new app or starting a big download can suddenly force other connections to close. If one person in your home reports constant drops during meetings or gaming while others are streaming, you may be running into the Starlink CGNAT limitation rather than a general outage or hardware failure.
Practical Ways to Work Around Starlink CGNAT Limits
You cannot raise Starlink’s 1,200-session ceiling on Residential and Roam plans, but you can reduce how often you hit it. First, tame background connections: close unused browser tabs, log out of idle VPNs, and limit always-on cloud sync on secondary devices. Consolidate services where possible—for example, use one VPN on your router instead of separate VPN apps on many devices. Schedule large downloads and backups outside peak usage or important meetings. On your home network, segment high-demand devices so you can switch off less critical gear during gaming or video calls. If you manage your own router, consider enabling IPv6 so more traffic bypasses IPv4 session limits. Finally, if problems persist, track when drops occur and how many devices are online; this evidence can help you and support staff confirm that the Starlink CGNAT limitation is the cause.
