topic Re: Minecraft Connectivity in IPv6 Trial

Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 14:44:18 GMT

Hi all,

Recently got onto the IPV6 trial and all seems good, however the kids have noted that Minecraft has stopped working.

It works if I disable IPV6 - so definitely an ipv6 issue

The (at least first) URL which is a problem is:

https://launcher.mojang.com/download/Minecraft.tar.gz (it's just downloading the initial installer at this point)

where the hostname resolves to 2603:1061:14:d4::1 and 150.171.109.215

I've tried just using wget on that and, after quite a bit of waiting, fails with: Unable to establish SSL connection.

Anyone else having similar issues? I've checked my firewalling, and nothing looks off - I'm wondering if it also might be a routing issue? Could someone else try, since my options to see if it works elsewhere are very limited!

Thanks

Re: Minecraft Connectivity

MJN — Fri, 01 May 2026 14:49:32 GMT

It seems okay for me:

$ wget -6 https://launcher.mojang.com/download/Minecraft.tar.gz
--2026-05-01 15:45:54-- https://launcher.mojang.com/download/Minecraft.tar.gz
Resolving launcher.mojang.com (launcher.mojang.com)... 2603:1061:14:d2::1
Connecting to launcher.mojang.com (launcher.mojang.com)|2603:1061:14:d2::1|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1102510 (1.1M) [application/x-gzip]
Saving to: ‘Minecraft.tar.gz.2’

Minecraft.tar.gz.2 100%[===================>] 1.05M --.-KB/s in 0.07s

2026-05-01 15:45:54 (15.4 MB/s) - ‘Minecraft.tar.gz.2’ saved [1102510/1102510]

I note I am resolving to a different IP address though so it could be a server-specific issue.

Re: Minecraft Connectivity

MJN — Fri, 01 May 2026 15:00:59 GMT

Given the SSL reference, does anything telling appear if you run openssl s_client -connect [2603:1061:14:d4::1]:443 which will show the SSL connection attempted being established.

Re: Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 15:04:43 GMT

Interesting - I get a different IP address each time (including the one you got), and same result.

I'll keep digging - thanks

Caroline

Re: Minecraft Connectivity

MJN — Fri, 01 May 2026 15:06:17 GMT

@CarrieSweetpea wrote:

Interesting - I get a different IP address each time (including the one you got), and same result.

Their servers are fronted by a content delivery network and so it'll just be down to the load balancing taking place.

Re: Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 15:31:21 GMT

Yeah, no, it connects, but doesn't establish the SSL connection at all. IPV4 for the same command immediately does all the TLS handshaking etc.

Re: Minecraft Connectivity

MJN — Fri, 01 May 2026 15:35:07 GMT

I wonder if there's an MTU issue? SSL certificates can certainly exceed a single packet in size.

Re: Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 15:48:32 GMT

MTU on the plusnet PPPoE connection is 1492, which looks as expected. If it was MTU, then I'd expect yourself to have similar issues (assuming you're going over the same PlusNet PPPoE server)

Re: Minecraft Connectivity

MJN — Fri, 01 May 2026 15:57:47 GMT

Yeah mine is set to 1492. It does still rely on Packet Too Big messages being able to get through though which might be the difference between us.

Re: Minecraft Connectivity

MisterW — Fri, 01 May 2026 16:04:36 GMT

@CarrieSweetpea are you running your own router or is it a Plusnet Hub 2 ?

Re: Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 16:21:10 GMT

Own router - Mikrotik E60iUGS

Re: Minecraft Connectivity

MisterW — Fri, 01 May 2026 16:35:43 GMT

Google 'icmp ipv6 pmtud discovery minecraft mikrotik' and check you have your firewall configured correctly

Re: Minecraft Connectivity

CarrieSweetpea — Fri, 01 May 2026 16:43:59 GMT

Awesome! Yup, that appears to have been the issue 5 year old reddit posts FTW

For posterity, this is what sorted it:

/ipv6 firewall mangle  
add action=change-mss chain=forward new-mss=clamp-to-pmtu passthrough=yes protocol=tcp tcp-flags=syn

Thanks!