Quote from: .anto. on January 31, 2016, 06:25:38 PM

I set 4 IPv6 addresses on the /64 subnet that I got from my providers. But I use only 1 IPv6 address for the node and I made sure that both incoming and outgoing Bitcoin packets use that particular IPv6 address via ip route and iptables settings.

According to what you mentioned, does this mean we should not set 2 different IP addresses on a single Bitcoin node even they are on different network, i.e. IPv4 and IPv6?

If you have single IPv6 address per interface then your IPv6 deployment is somewhat nonstandard. The canonical way of deploying IPv6 is with at least two IPv6 aliases per interface: one "permanent" and at least one "temporary" that is changed on a regular schedule. The "permanent" is mostly for incoming connections, the "temporary" is mostly for outgoing connections. If you have man long-lasting outgoing connections (like e.g. Bitcoin, unlike e.g. HTTP) you should have multiple simultaneous "temporary" IPv6 addresses active on the interface.

There are so many Linux distributions that I can't give you the specifics for yours. I happen to know that Windows do come out of the box with well optimized canonical IPv6 setup. However if you really want to understand what is going on locally with your node you will have to delve into reading the Bitcoin source.

As far as Bitnodes they are not to be 100% trusted. They have been subject to Sybill attacks by people trying to game the node version statistics. They deployed some secret anti-Sybil and anti-DDoS code with the net effect that they undercount the real reachable nodes. This is a well known and well discussed issue with Bitcoin: the nodes really mean nothing without proof-of-work. So there's no easy, simple, obviously right way of counting Bitcoin peers. It really depends on the particular configuration of your machine as well as on the configurations of any possible Bitcoin peers using the same ISP as you.