Multiple /64 ULA subnets sharing same WAN /64 prefix via NPTv6?



  • My ISP only route single /64 subnet to resident connection. I'm planning to deploy ULA for each of my VLANs and then NPT to that public /64 prefix assigned by ISP. Do I need to worry about suffix conflict?

    Is there any drawbacks (e.g. latency...) in deploying ULA + NPt compared to just GUA via Track interface? The only problem i can think of is that I would need to manually adjust NPt entries every time my ISP routed prefix change.



  • @nva

    Do they really provide only a single /64? Or is your modem in gateway mode and not bridge mode? If I have my modem configured as a gateway, I get a single /64. If it's in bridge mode, I get a /56 which pfSense can split into up to 256 /64s.



  • @JKnott It's definitely dynamic /64, ISP tech confirmed that to me. ISP modem is in bridge mode. They have plans with /56 static prefixes but I'd have to pay twice the price for same bandwidth.



  • @nva said in Multiple /64 ULA subnets sharing same WAN /64 prefix via NPTv6?:

    They have plans with /56 static prefixes but I'd have to pay twice the price for same bandwidth.

    It's amazing how CHEAP some ISPs are, considering the IPv6 address space is so vast. While my ISP initially provided a single /64, that was only temporary and they soon moved to /56. Then there's he.net, which will provide a /48 for free! Before my ISP offered IPv6, I used a tunnel and got a /56 again for free.

    BTW, the address space is so vast that every single person on earth could have over 4000 /48s and that's with only 1/8th of the entire address space assigned to anything.



  • @nva said in Multiple /64 ULA subnets sharing same WAN /64 prefix via NPTv6?:

    It's definitely dynamic /64

    ISPs, including mine, commonly use DHCPv6-PD to provide the prefix. While not officially static, it essentially is, as my prefix is tied to my DUID.


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