What is Teredo?

[#1]

I found some entries in my router's firewall > port forwarding that I'm sure weren't there before:

Are they normal or I should worry?

Not sure if related, but I'm using (from time to time) a VPN service on my DESKTOP. However, kobo (in the list) is just a e-reader, so never needed a VPN. So what's with the firewall entries? Who's creating them?

[#2]

I found this on Wikipedia....

In computer networking, Teredo is a transition technology that gives full IPv6 connectivity for IPv6-capable hosts that are on the IPv4 Internet but have no native connection to an IPv6 network. Unlike similar protocols such as 6to4, it can perform its function even from behind network address translation (NAT) devices such as home routers.

Toredo Tunneling

[#3]

The green tick for each rule indices UPnP (universal plug and play) setup a port forward.

Teredo from what I can see is a IPv6 to IPv4 tunnelling software which looks to be installed on four of your devices (one rule for each device)

kobo will be the device/host name

[#4]

"Christian Huitema developed Teredo at Microsoft, and the IETF standardized it as RFC 4380. The Teredo server listens on UDP port 3544."

I could be wrong, but my understanding is that it takes a TCP connection and wraps it within a UDP packet (possibly why UPnP is part of the question, and that's how it tunnels). Possible firewalling implications when the firewall isn't on the source hardware.

Since it was developed within Microsoft, I can't help but say that Micosoft have enough trouble following their own standards.

[#5]

So.... should I worry or not?

What I still don't understand is how or what is creating the entries in the router's firewall. Or is it the router itself doing these?!

Can't be my devices, the Kobo is just a reader and there is also PS5 in the list. Further more, 1-2 years ago I don't remember seeing these entries there.