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IPv6

    Question

  • Hi all,

    when I run ipconfig/all on a ipv6 host, it will show only its ipv6 prefix related to that computer.

    Is it possible to see or find the whole(128_bit) ipv6 completely?

    thanks

    Monday, September 30, 2013 7:40 PM

Answers

  • The Link-Local address (actually focusing on the Interface ID [IID] portion [aka host ID], last 64bits) you are seeing is not derived based on the modified EUI-64 format RFC-4291, it is derived based on the Privacy Extensions (random number generator) format RFC-4941.

    The quickest way to know this to be the case, if it were a Link-Local address based on M-EUI-64 format, you would see the addr to look more like 'fe80::8a9f:75ff:fe75:a436' with the "ff:fe" in the middle of the 64bit Interface ID of the address. Since you don't see the "ff:fe", it is a fair assumption that the IID was derived via a random number generator.

    Microsoft starting in Windows Vista and Windows Server 2008 choose the Privacy Extensions method as its default way to derive the IID, as it is considered a more "secure" IID, since the MAC address is not embedded in the IID. Note, this default method can be changed to the M-EUI-64 format.

    Read Ch7 of Guide to TCP/IP, 4th Edition for more detail on this topic.

    hth...Jeff


    Jeff Carrell

    • Marked as answer by mahdy-fr Tuesday, November 12, 2013 8:02 PM
    Sunday, November 03, 2013 2:06 PM

All replies

  • ???

    If you could post the output of what you are seeing, it would be easier to answer.

    When I run same command, I get all the info, IPv6 Link-Local addr and any/all of the IPv6 Global Unicast addr.

    Let us know...Jeff


    Jeff Carrell

    Thursday, October 03, 2013 10:47 PM
  • Wireless LAN adapter Wireless Network Connection:

       Connection-specific DNS Suffix  . :
       Description . . . . . . . . . . . : Atheros AR9285 Wireless Network Adapter
       Physical Address. . . . . . . . . : 88-9F-FA-75-A4-36
       DHCP Enabled. . . . . . . . . . . : Yes
       Autoconfiguration Enabled . . . . : Yes
       Link-local IPv6 Address . . . . . : fe80::317f:d8e3:7b3:81fd%29(Preferred)

    I studied related /64 bit to interface-id calculated from mac address.

    Is this issue correct in the above example?

    b.rgds

    Saturday, November 02, 2013 6:12 PM
  • The Link-Local address (actually focusing on the Interface ID [IID] portion [aka host ID], last 64bits) you are seeing is not derived based on the modified EUI-64 format RFC-4291, it is derived based on the Privacy Extensions (random number generator) format RFC-4941.

    The quickest way to know this to be the case, if it were a Link-Local address based on M-EUI-64 format, you would see the addr to look more like 'fe80::8a9f:75ff:fe75:a436' with the "ff:fe" in the middle of the 64bit Interface ID of the address. Since you don't see the "ff:fe", it is a fair assumption that the IID was derived via a random number generator.

    Microsoft starting in Windows Vista and Windows Server 2008 choose the Privacy Extensions method as its default way to derive the IID, as it is considered a more "secure" IID, since the MAC address is not embedded in the IID. Note, this default method can be changed to the M-EUI-64 format.

    Read Ch7 of Guide to TCP/IP, 4th Edition for more detail on this topic.

    hth...Jeff


    Jeff Carrell

    • Marked as answer by mahdy-fr Tuesday, November 12, 2013 8:02 PM
    Sunday, November 03, 2013 2:06 PM
  • The IPCONFIG output is displaying the whole IPv6 address, it is just displaying with zero compression/suppression.

    In the address fe80::317f:d8e3:7b3:81fd the two colons represent enough additional zeros to fill out the entire 128 bits. The full address without zero compression/suppression is:

    fe80:0000:0000:0000:317f:d8e3:07b3:81fd

    I hope this helps.

    Ed

    Sunday, November 10, 2013 3:42 AM
  • hi Jeff

    thanks alot.

    Tuesday, November 12, 2013 8:02 PM