IPv6 Prefix ID vs DHCPv6 Prefix Delegation size



  • I've noticed something curious.  On the WAN side a /48 prefix (65536 /64s) can be selected.  However, on the LAN side, the highest Prefix ID available is ff, which would limit the number of available networks to 256 (/56 prefix), instead of the 65536 available with a /48.  Is there any reason for this discrepancy?



  • So are you really going to create over 256 networks from local interfaces or VLANs on your pfSense box? I get the feeling that creating a dropdown list with over 65,000 list items in it would be likely to crash a browser, so they opted to limit the drop-down to a maximum of 256 items. Not to mention the load time of the page as all that HTML is generated and downloaded.

    Now someone needs to get the prefix delegation in the DHCPv6 Server working with Track Interface setups so you could sub-delegate the rest of that /48 to downstream routers.



  • I wasn't planning on having over 256 interfaces.  However, since the WAN config allows a /48, but the prefix ID supports no more than a /56, it implies you could get a larger prefix than you could use.  If you can't assign more than 256 prefixes, then perhaps the WAN prefix size should be limited to /56.  It might be useful if each interface could be larger than a /64, for further routing, but I don't see that available.


  • Netgate

    Now someone needs to get the prefix delegation in the DHCPv6 Server working with Track Interface setups so you could sub-delegate the rest of that /48 to downstream routers.

    I would argue that ISPs need to get with the program and statically route /48s like they're supposed to.



  • I can understand why ISPs might not want to statically assign non-business customer prefixes, as the customers may come and go.  However, through the use of the DUID, the assigned address should not change, at least not for the lifetime of the DUID.