Home Networking

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I'm under CG-NAT and DHCP but port forwarding worked, why? (alien.top)

submitted 11 months ago by [email protected] to c/[email protected]

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After learning about CG-NAT and DHCP, in hindsight I'm wondering why it worked. I got a few ideas why but could someone explain?

Was it because it was all within LAN, and not remotely from outside LAN? So anything within LAN will work even under CG-NAT?

Was it because it was just the PC and the router, and doing something like sshing into PC from phone would've not worked? I.e, device-to-device wouldn't work but device-to-router does?

Was it because I have both ipv4 and ipv6 (according to wifi settings on my phone), and ipv6 isn't affected by CG-NAT?

I can't remember exactly what the issue DHCP brings for port forwarding, remote access, ssh, etc. is but I feel like there was something and the solution was static IP or DDNS. Might've been a selfhosting thing? idk

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[–] [email protected] 1 points 11 months ago

CGNAT affects accessing your LAN from outside your network, i.e. over the Internet. Traffic within your own LAN is not affected whatsoever.

[–] [email protected] 1 points 11 months ago

Try access it using mobile data.

Local will work because it is your network. Outside of that depends on ISP.

[–] [email protected] 1 points 11 months ago

A LAN works without the Internet at all. CG-NAT is the internet for you. So anything LAN related is free of cg-nat restrictions.

DHCP could change your internal IP, so it's nice to have static IPs sometimes.

[–] [email protected] 1 points 11 months ago

It is possible your router supports hair-pinning or (NAT loopback).

When it detects you are trying to access the external IP address (even if it is cg-nat) it is smart enough to router the data basin internally and some are smart enough to apply firewall rules as well...