I recently spent quite a bit of time trying to run my Valheim dedicated server over native IPv6 because my ISP uses CGNAT and does not provide a public IPv4 address.
The frustrating part is that Valheim is already very close to supporting this properly.
I was able to run the dedicated server without -crossplay and successfully connect directly to it using its public IPv6 address on UDP 2456. I also confirmed an external player could connect over native IPv6. Packet captures showed traffic reaching the server and replies coming from the correct IPv6 address.
I set up a DuckDNS hostname with an AAAA record pointing directly to the server:
name -> public IPv6
Public DNS resolution worked correctly, the OpenWrt firewall allowed UDP 2456-2458 over IPv6, and the Ubuntu server had normal native IPv6 connectivity. No NAT or port forwarding was involved.
Unfortunately, the experience isn't reliable enough to actually use. Valheim's Join IP functionality seems inconsistent with AAAA-only hostnames. Some clients reported "DNS lookup failed" despite the AAAA record resolving correctly through public DNS servers. Directly entering the IPv6 address worked for some players, while another player couldn't connect at all. Server discovery also doesn't appear to be fully IPv6-friendly.
I eventually gave up and switched back to -crossplay. PlayFab works reliably, but now we're back to temporary join codes that change whenever the server restarts.
It would be great if dedicated servers had proper first-class IPv6 support:
- Reliable AAAA hostname resolution in Join IP
- Reliable direct connections to IPv6 addresses
- IPv6-compatible server discovery
- Consistent IPv6 support across clients
- Ideally, the ability to use a normal hostname with crossplay rather than depending on changing join codes
IPv4 CGNAT is increasingly common, and IPv6 is exactly what solves this problem. Valheim's networking already appears capable of carrying the actual game traffic over IPv6. It just needs the rest of the dedicated-server/client stack to support it consistently.
I'd happily use native IPv6 instead of PlayFab if it were officially supported and reliable.
Source: r/valheim · by /u/Swifttree