Inbound connections when there should be none

[RedGolpe]

I have my Bitcoin Core client up and running almost constantly but from time to time, when I need more resources, I disable inbound connections by removing the relevant port mapping on my router. It may or may not be relevant that my router does not support UPnP but I have it enabled on the client.

I check if I'm actually reachable with bitnodes, and it says I'm visible or not depending on the port mapping settings so everything seems to work as expected.

However, even when I am "invisible" to the network, I receive inbound connections. I generally end up with one or two of them, always with a IPv6 address: how is that possible?

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[shorena]

I have my Bitcoin Core client up and running almost constantly but from time to time, when I need more resources, I disable inbound connections by removing the relevant port mapping on my router. It may or may not be relevant that my router does not support UPnP but I have it enabled on the client.

I check if I'm actually reachable with bitnodes, and it says I'm visible or not depending on the port mapping settings so everything seems to work as expected.

However, even when I am "invisible" to the network, I receive inbound connections. I generally end up with one or two of them, always with a IPv6 address: how is that possible?

Sounds like your router does not respect the settings for ipv6. Is there another set of rule for those connections maybe?

[Foxpup]

IPv6 typically doesn't use NAT, so other nodes can connect to you directly without port mapping. Does Bitnodes say you're reachable when you enter your IPv6 address?

In any case, you can disable inbound connections on all networks by starting Bitcoin Core with the listen parameter set to 0 (either on the command line or in bitcoin.conf). You can also limit the total number of connections with the maxconnections parameter.

[shorena]

IPv6 typically doesn't use NAT, so other nodes can connect to you directly without port mapping.

Yeah, would be a firewall setting on the router explicitly blocking the port.

[RedGolpe]

Thank you for all your answers, it surely must be an IPv6 setting, I will try with my IPv6 address on Bitnodes.

Edit: confirmed.