IPv6 Unicast Address

Answered Question
Apr 25th, 2010
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The answer for the question below is 3.

Why can't 4 be a valid unicast address?


Which address is a valid IPv6 unicast address?

1.    FE90::1::FFFF

2.    FD80::1::1234

3.    FE80::1:4545:6578:ABC1

4.    FEA0::100::7788:998F

5.    FC90::::5678:4251:FFFF

Correct Answer by mlund about 7 years 4 days ago

Hi


Taken the same example as Ganesh.


2001:cdba:0000:0000:0000:0000:3257:9652
2001:cdba:0:0:0:0:3257:9652

2001:cdba::3257:9652

this example shows how You can group a set of zeroe's together and write it as :: instead.


However this double :: can only be present once, so an address written as

2001:cdba:0:0:1:0:0:9652 can be written either as
2001:cdba:0:0:1::9652 or

2001:cdba::1:0:0:9652 but not

2001:cdba::1::9652


In question 1,2 and 4 there are two groups of :: , this is not valid, and in q5 it's written ::::, wich is also not a legal address.


/Mikael

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Ganesh Hariharan Sun, 04/25/2010 - 23:09
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The answer for the question below is 3.

Why can't 4 be a valid unicast address?


Which address is a valid IPv6 unicast address?

1.    FE90::1::FFFF

2.    FD80::1::1234

3.    FE80::1:4545:6578:ABC1

4.    FEA0::100::7788:998F

5.    FC90::::5678:4251:FFFF


Hi,


Answers 3 is correct is because fe80::/10  is a link-local prefix offered by IPv6. This address prefix signifies that the address is valid only in the local physical link.An IPV6  Unicast address acts as an identifier for a single interface. An IPv6 packet sent to a Unicast address is delivered to the interface identified by that address.IPv6 addresses are denoted by eight groups of hexadecimal quartets separated by colons in between them.


Following is an example of a valid IPv6 address: 2001:cdba:0000:0000:0000:0000:3257:9652

Any four-digit group of zeroes within an IPv6 address may be reduced to a single zero or altogether omitted. Therefore, the following IPv6 addresses are similar and equally valid:


2001:cdba:0000:0000:0000:0000:3257:9652
2001:cdba:0:0:0:0:3257:9652

2001:cdba::3257:9652


Network Notation in IPV6 follows the below example


2001:cdba:9abc:5678::/64 denotes the network address 2001:cdba:9abc:5678. This network comprises of addresses rearranging from 2001:cdba:9abc:5678:: up to 2001:cdba:9abc:5678:ffff:ffff:ffff:ffff. In a similar fashion, a single host may be denoted as a network with a 128-bit prefix. In this way, IPv6 allows a network to comprise of a single host and above.


Hope to Help !!


Remember to rate the helpful post


Ganesh.H

leepeiwai Mon, 04/26/2010 - 01:48
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Ganesh, Thanks for your reply.


However, my question is why 4.(FEA0::100::7788:998F) is not a valid unicast IPv6?

I read that IPv6 private addresses begin with FE, and follow with 8 to F.

Therefore, all 1,3,4 can be unicast address?


1.    FE90::1::FFFF

2.    FD80::1::1234

3.    FE80::1:4545:6578:ABC1

4.    FEA0::100::7788:998F

5.    FC90::::5678:4251:FFFF

Ganesh Hariharan Mon, 04/26/2010 - 02:55
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Ganesh, Thanks for your reply.


However, my question is why 4.(FEA0::100::7788:998F) is not a valid unicast IPv6?

I read that IPv6 private addresses begin with FE, and follow with 8 to F.

Therefore, all 1,3,4 can be unicast address?


1.    FE90::1::FFFF

2.    FD80::1::1234

3.    FE80::1:4545:6578:ABC1

4.    FEA0::100::7788:998F

5.    FC90::::5678:4251:FFFF


Hi,


A link-local unicast address has the prefix fe80::/10 in standard IPv6 addressing scehme and following are the cases with meaning of address used


2001:db8::/32 This is a documentation prefix allowed in the IPv6. All the examples of IPv6 addresses should ideally use this prefix to indicate that it is an example.
fec0::/10 This is a site-local prefix offered by IPv6. This address prefix signifies that the address is valid only within the local organization. Subsequently, the usage of this prefix has been discouraged by the RFC.

fc00::/7 This is called the Unique Local Address (ULA). These addresses are routed only within a set of cooperating sites. These were introduced in the IPv6 to replace the site-local addresses. These addresses also provide a 40-bit pseudorandom number that reduces the risk of address conflicts.

ff00::/8 This prefix is offered by IPv6 to denote the multicast addresses. Any address carrying this prefix is automatically understood to be a multicast address.

fe80::/10 This is a link-local prefix offered by IPv6. This address prefix signifies that the address is valid only in the local physical link.


Check out the below link for address scehme


http://www.6diss.org/workshops/saf/addressing.pdf


Hope to help !!


Ganesh.H


Remember to rate the helpful post

Correct Answer
mlund Mon, 04/26/2010 - 04:34
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Hi


Taken the same example as Ganesh.


2001:cdba:0000:0000:0000:0000:3257:9652
2001:cdba:0:0:0:0:3257:9652

2001:cdba::3257:9652

this example shows how You can group a set of zeroe's together and write it as :: instead.


However this double :: can only be present once, so an address written as

2001:cdba:0:0:1:0:0:9652 can be written either as
2001:cdba:0:0:1::9652 or

2001:cdba::1:0:0:9652 but not

2001:cdba::1::9652


In question 1,2 and 4 there are two groups of :: , this is not valid, and in q5 it's written ::::, wich is also not a legal address.


/Mikael

leepeiwai Mon, 04/26/2010 - 14:42
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Thanks Ganesh and Mikael for your explaination.

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