Valid IPv6 address

Answered Question
Apr 9th, 2010
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Hi all,


I was studying for cisco exam and there is question if this address is valid IPv6 or not


2002:7654:a1ad:61:81af:ccc1


any answers


thanks

mahesh

Correct Answer by Giuseppe Larosa about 7 years 1 month ago

Hello Mahesh,

an IPv6 address is made of 128 bits and it is represented using exadecimal digits.


Each hex digits represents 4 binary digits  = 1 hex = 4 bits


So an IPv6 address is made of 128/4 = 32 hexadecimal digits


the usual hex dotted representation groups 4 hex and separate these groups using a ':'


So an IPv6 address is made of 8 4hex groups divided by :


the notation allows to represent one of more 4 hex consecutive groups made of all zeroes with a ::

This can appear only once in the number.


In your case the proposed hexadecimal sequence is:


2002:7654:a1ad:61:81af:ccc1


2002:7654:a1ad:0061:81af:ccc1


Here we see only 6 4-hex groups, no :: appears in the middle to represent all zero groups so it is too short.


an IPv6 prefix is represented with a final ::/prefix length


this is not a valid IPv6 address because it is too short, it could be an IPv6 prefix if written as:


2002:7654:a1ad:61:81af:ccc1::/96


see

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-addrg_bsc_con.html#wp1027186


Hope to help

Giuseppe

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Correct Answer
Giuseppe Larosa Fri, 04/09/2010 - 11:36
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Hello Mahesh,

an IPv6 address is made of 128 bits and it is represented using exadecimal digits.


Each hex digits represents 4 binary digits  = 1 hex = 4 bits


So an IPv6 address is made of 128/4 = 32 hexadecimal digits


the usual hex dotted representation groups 4 hex and separate these groups using a ':'


So an IPv6 address is made of 8 4hex groups divided by :


the notation allows to represent one of more 4 hex consecutive groups made of all zeroes with a ::

This can appear only once in the number.


In your case the proposed hexadecimal sequence is:


2002:7654:a1ad:61:81af:ccc1


2002:7654:a1ad:0061:81af:ccc1


Here we see only 6 4-hex groups, no :: appears in the middle to represent all zero groups so it is too short.


an IPv6 prefix is represented with a final ::/prefix length


this is not a valid IPv6 address because it is too short, it could be an IPv6 prefix if written as:


2002:7654:a1ad:61:81af:ccc1::/96


see

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-addrg_bsc_con.html#wp1027186


Hope to help

Giuseppe

mahesh18 Fri, 04/09/2010 - 13:28
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Hi giuslar,


many thanks for correct reply


regards

mahesh

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