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What is the lowest IPv6 host address in an address range; is it A:B:C:D:E:F:0:0/64 or A:B:C:D:E:F:0:1/64? Does IPv6 have a network address (0 = "this") like IPv4? I know one address type is depricated in IPv6, but I can't remember which one.

My copy of Douglas E. Comers' "Internetworking with TCP/IP Vol.1: Principles, Protocols, and Architecture (4th Edition)" is a few hundred kilometres away, so I can't check.

  • A, B, C, D, E, and F do not denote hexadecimal numbers, but rather unknown numbers.
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I suppoe I can use A:B:C:D:E:F:0:0 if the subnet is trully /64, because all 2^16 IPv6 IPs I've been assigned are, basically, host addresses. Opinions? – nlovric Feb 13 '12 at 4:25
On a side note, after deciding to use A:B:C:D:E:F:0:0 as the IPv6 address using your opinions, I am now waiting for my DNS provider to solve their DNS returning random AAAA records for my server. – nlovric Feb 13 '12 at 13:29
up vote 3 down vote accepted

The XYZ::0 address (where the host part of the address is set to all 0s) is the subnet-router anycast address.

See Linux IPv6 loopback routes getting automatically added where I discovered that although you can use a ::0 address on some equipment (e.g. Cisco), it breaks other equipment (like Linux).

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Both work for me, but I was unsure whether it was the result of anycast or unicast. Is A:B:C:D:E:F:0:0/64 an anycast or a unicast address? – nlovric Feb 13 '12 at 4:59
F is not 0. [text to fullfill the minimal comment length requirement] – nlovric Feb 13 '12 at 5:05
That is a unicast address (all else being equal, i.e. the block not being an anycast/multicast block). – Zanchey Feb 13 '12 at 5:23
Wow, you learn something new everyday, indeed the ::0 address is responded to by the (linux) router. I've seen ::0 addresses in use as destination, such as http://[2600::]/ for a sprint webserver which still works. points to 2600::aaaa. – Koos van den Hout Feb 18 '12 at 17:37

It might be important to note that while Zanchey's answer is correct with regards to x::0 hosts, the example in the question does not describe a ::0 host.

The example was A:B:C:D:E:F:0:0/64. A:B:C:D is the network portion, and the host address is actually E:F:0:0, not 0.

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