| upper case and lower case letters in Ipv6 hi
I was wondering if there is a difference between upper case letter an lower case letter in an IPv6 address: Example is below would these two IP blocks be the same or different?
123Z:123V:1A1A:1234:256A:252B::/64
123z:123v:1a1a:1234:256a:252b::/64
There are a few websites saying that this is different from each other and few websites saying that they are the same address.
Thank you
K |
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 leiboldPremium,MVM
join:2002-07-09
Sunnyvale, CA
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 ·SONIC.NET
·Pacific Bell - SBC
| It doesn't really matter whether they are the same or different, because neither are valid IPv6 addresses 
Upper and lower case characters are really only an issue in the text representation of an IPv6 address. The wireline format is a bunch of 0s and 1s and an uppercase 'A' and a lowercase 'a' are both representing the bit sequence 1010.
Software that accepts IPv6 addresses in text format should accept upper and lower case characters and treat them as equal. RFC 5952 states that when actual IPv6 addresses are being converted into the text format that lowercase characters shouldmust be used.
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| Thank you... That was just an example of Ipv6 address that is bad
So it doesn't matter
Thanks |
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 Wily_OnePremium
join:2002-11-24
San Jose, CA | reply to krock83
Back when I learned hex, we used uppercase A-F; ...maybe part of the reason was back in those days most character generators only did uppercase. To this day I have a hard time getting used to using lowercase in MAC addresses and now IPv6 addresses. |
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leiboldPremium,MVM
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Sunnyvale, CA
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| If you look at the IPv6 addressing standards (RFC3513/RFC4921) you will see uppercase characters used exclusively
To krock83  , it shouldn't matter. There will always be poor software implementations that will do simple string comparison on IPv6 addresses in text format who will not only be misled by upper and lower case characters but also by IPv6 address that are in full and short form.
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| reply to krock83
RFC 5952 indicates that ipv6 addresses should be represented in lower case.
»tools.ietf.org/html/rfc5952#section-4.3 |
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leiboldPremium,MVM
join:2002-07-09
Sunnyvale, CA
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| said by lestat99:RFC 5952 indicates that ipv6 addresses should be represented in lower case. This is correct. However RFC 5952 is sometimes misinterpreted as making it mandatory that IPv6 addresses use lower case characters and it does no such thing.
said by "RFC 5952 Section 4" :The recommendation in this section SHOULD be followed by systems when generating an address to be represented as text, but all implementations MUST accept and be able to handle any legitimate [RFC4291] format. RFC 5952 recommends (and gives good reasons for such a recommendation) to use lower case characters in the text representation of IPv6 addresses (as well as other rules on address formatting). For the input of IPv6 addresses in text format RFC 5952 refers to the IPv6 addressing standard RFC4291 and clearly states that all legitimate formats (and that includes upper case characters) must be accepted.
Note that there is an Errata for RFC 5952 (Errata #2656) that makes a good case for using upper case instead of lower case characters in the recommended format. The decision to use lower case characters in RFC 5952 is controversial, but given the widespread implementation of code that formats IPv6 addresses with lower case characters I doubt this Errata will get verified.
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