Do I have a /56 or /60



  • My WAN is configured for DHCPv6 with a delegation size of 60 with "send prefix hint" selected. I have two internal subnets which track the WAN and each get their own IPv6 prefix. I expected them to get their own prefixes on the same /60. But, the only thing they each have in common is the first 56 bits. Does this mean I have a /56 subnet from my provider? If I switch the WAN desired delegation size to 56 I get no IP6 previx on the tracking interfaces. I'm confused by the selection of the desired delegation size. What does it do exactly and why doesn't it represent what I get?

    LAN1: 2601:2:4e88:ee0:
    LAN2: 2601:2:4e88:ee1:

    Did I count the bits correctly?



  • Your /60 prefix should be  2601:2:4e88:ee8::  2601:2:4e88:ee0::

    You can view that here:  /var/dhcpd/etc/dhcpdv6.conf

    Take that prefix and plug it in here:  http://www.gestioip.net/cgi-bin/subnet_calculator.cgi

    Making the available /64's:

    2601:2:4e88:ee0::/64  
    2601:2:4e88:ee1::/64
    2601:2:4e88:ee2::/64
    … etc

    If you are Comcast residential,  requesting a /56 will get you nothing.



  • @priller:

    Your /60 prefix should be 2601:2:4e88:ee8::

    I believe that should be 2601:2:4e88:ee0::, no?



  • @rkcin:

    LAN1: 2601:2:4e88:ee0:
    LAN2: 2601:2:4e88:ee1:

    Note that the numbers within each group are "right-aligned." I.e., these prefixes are exactly the same as the following:

    
    LAN1: 2601:0002:4e88:0ee0::
    LAN2: 2601:0002:4e88:0ee1::
          ^^^^ ^^^^ ^^^^ ^^^
    
    

    Each digit represents four bits; if you compare the two prefixes, you'll see that their leftmost 15 digits match, so they're in the same /60.



  • @razzfazz:

    @priller:

    Your /60 prefix should be 2601:2:4e88:ee8::

    I believe that should be 2601:2:4e88:ee0::, no?

    Agh!  Thx



  • Yes, thank you. That's where I went wrong. I see it now.


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