Hey everyone! I'm trying to figure out how to utilize the /56 IPv6 prefix that Comcast Business assigned to me. I want to use it similarly to how I would with my IPv4 block, but I'm running into issues. When I set up my router's interface for the IPv6 prefix, whether it's :1/64, :1/128, or the general ::/56, I'm not able to get anything to show up on the public internet. Can someone help clarify how I can make use of this? Thanks!
4 Answers
You set /64s to subnets by tracking the interface for IPv6. Devices can learn their addresses via SLAAC from router advertisements or use DHCPv6 if you prefer. Then, create an alias under firewall-aliases that updates dynamically with your prefix change. Standard firewall rules should then apply to expose your services, like web traffic on ports 80/443.
I also have an Opnsense box behind the Comcast router. They limit me to pulling a /59, which I distribute to different VLANs as /64s. If I try for anything larger than /59, I end up with nothing. Make sure your devices request a /64; they could get addressed from random /59s on a Comcast modem reboot. You might find ways to pull multiple /59s with some editing in Opnsense, but I’ve never needed that. Check out this forum for more info: https://forum.opnsense.org/index.php?topic=30806.0
Is your IPv6 a Static or Dynamic allocation? If it’s Dynamic, you’ll need to request a /56 via Prefix Delegation using DHCPv6. For Static, you should have a Transit (or Point to Point) address besides the /56 subnet. Assign your router a static IP from the /126 and set it up to match the Gateway IP at Comcast, just like for IPv4. After that, subnet your /56 into /64s for your LAN devices.
Good luck! Just take your time getting it all set up. If you hit more snags, feel free to ask here again.
You might want to check out how OpenWRT handles this. After dealing with issues on a Ubiquiti Edgerouter, switching to OpenWRT worked seamlessly for me. Just a heads up, I’ve only done this on my home Comcast Business setup for practice, so I'm not using it for work just yet since I’m wary of causing issues due to mistakes or Comcast changing things.
Could you point me to a specific OpenWRT configuration discussion? I’m not familiar with it for core routing and didn’t think it would be a viable option for my situation.
Sure! There are plenty of resources available at the OpenWRT forums and their official wiki. It could help you get started.
Thanks for your insights! I suspect my "static" account is actually dynamic due to what I've seen from Comcast. They haven’t given me any info on the gateway setup, making this whole process frustrating. I’ll get back to configuring my test setup soon and share my progress.