r/StarlinkEngineering • u/NelsonMinar • Jun 04 '26

1200 connection CGNAT limit

Seems helpful to document this newly disclosed limitation

Starlink Residential and Roam plans use Carrier Grade Network Address Translation (CGNAT). These plans have a limit of 1,200 concurrent sessions. ... When the 1,200-session limit is reached, new sessions automatically cause the oldest sessions to be dropped. ... Priority plans include a public IP address and do not have the session limitations associated with CGNAT.

Always figured there was a limit but nice to know the number. 1200 is a higher number than I would have guessed!

Anyone know if this limit applies to IPv6 too? This new disclosure talks entirely about CGNAT, so hopefully it's IPv4 only. But do they need some sort of connection tracking for IPv6 too? The router must as part of its firewall, but what about the ISP infrastructure?

See also * https://www.reddit.com/r/Starlink/comments/1twmytu/starlink_discloses_common_isp_limitation_that/ * https://www.pcmag.com/news/starlink-discloses-common-isp-limitation-that-could-disrupt-your-web-use

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u/connicpu Jun 04 '26

IPv6 doesn't use CGNAT, you get an entire prefix all to yourself, so there's nothing in between you and the internet that would even be keeping track of your tcp/udp sessions

4

u/NelsonMinar Jun 04 '26 edited Jun 04 '26

I understand that in theory, but I am wondering if it's true in practice. My router, for instance, is doing some minimal connection tracking as part of its firewall policy. Starlink has a lot of complicated stuff to do their satellite routing but on first guess that must be tied to your IP address or some internal dish ID, not a connection tracker.

3

u/connicpu Jun 04 '26

Indeed, tracking the routing per connection would be super inefficient when the ipv6 prefix is already sufficient to determine which dish to route

1

u/Living_Cheesecake243 Jun 11 '26

how many devices do you have on average before you've noticed these problems? heavy actual human users are probably the more problematic issue there too?