just for "fun" route a /80 Prefix?



  • My question, is it doable to configure some Interfaces with for example a /80 Prefix and to manually assign the IP-addresses on those hosts? pfSense would still route this fine or what do you think?
    And would the DHCPv6-Server work? I read, this is probably not the case.

    The idea came up, because my ISP is only giving out one /64 prefix. So maybe it is not just for the fun. 😉



  • @Bob-Dig

    You can use whatever size prefix you want, but don't expect things to work. IPv6 is built around 64 bits for the network part of address and 64 for the host part. About the only exception would be point to point links, where you can use a /127. Also, /128 is often used to identify an interface. As far as I know, a DHCPv6 server will only provide a /64 to a LAN.



  • @JKnott said in just for "fun" to route a /80 Prefix?:

    As far as I know, a DHCPv6 server will only provide a /64 to a LAN.

    Or the clients will not accept anything other...
    I am even thinking about using NPt, because the prefix from my isp is dynamic.



  • @Bob-Dig said in just for "fun" to route a /80 Prefix?:

    I am even thinking about using NPt, because the prefix from my isp is dynamic.

    Normally, you retain the same prefix with the Do not allow PD/Address release set. However, if you're worried about maintaining addresses on your LAN, you could consider Unique Local Addresses, so that you don't have to worry about the prefix changing. You can have both ULA and global addresses on the same network, as I do here.



  • @JKnott First, I found another guy with the same ISP and the same problem at another forum. He is working in IT, I am not and he thought about doing it, but he has not pfSense as a router, but I have and so I am thinking: I will try that.

    Because I got the HE-Tunnel I have more then enough addresses for myself anyway.

    So I think I have to manually assign that ULA and then do NPt. Wish me luck @JKnott



  • @Bob-Dig

    No, you do not use NPt. Using ULA means the addresses for local devices will never change, unless you want them to. Since you can have both ULA and GUA on the LAN, Internet access still works fine. The only concern would be if you wanted to make a server publicly available. Also, with he.net, your prefix shouldn't change, so why are you having that problem? Also is that setting I mentioned selected?

    As I mentioned, I use ULA here. I have my DNS server configured to use the ULA address for local devices, though the GUA is used on the external DNS.



  • @JKnott I am talking only about my isp-IPv6 here, not HE and in the end it is not for me but the other guy. And I will try NPt because of the dynamic IPv6-Prefix...



  • So my testing is not as easy as I hoped... I found out, that I had a static route in one of my machines to use the he tunnel... I didn't made this, but had to delete it manually, another first timer for me I guess.



  • So I finished my testing somewhat successful.
    I divided that one and only /64 Prefix from my pesky ISP into some /80s. All my PCs, physical and virtual (Windows 10, Ubuntu Server 18.04) worked fine with that /80s, tested from inside and outside.
    My older Asus-Router, configured as an AP, my Android10-Phone, connected to that AP, and my Dell MuFu-Printer, connected via Ethernet, stayed on IPv4 only.
    Not the worst outcome I think.
    So it is doable, but not for every device.

    NPt with that ULA seemed to work also for one interface, for one other it wasn't at the time of testing, so I skiped this test, to later find out, that there was this bad static-route... So my conclusion, although not thoroughly tested, it would be working with ULA and NPt the same as with direct public IPv6 Prefixes. 👍


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