Comments on: IPv6 Addressing http://blogs.cisco.com/security/ipv6-addressing/ Sat, 25 May 2013 19:32:29 +0000 hourly 1 By: Earl Carter http://blogs.cisco.com/security/ipv6-addressing/#comment-146852 Earl Carter Mon, 25 Apr 2011 19:53:18 +0000 http://blogs.cisco.com/?p=23506#comment-146852 With modified EUI-64 addresses, the universal/local bit is inverted with
the intent that a ’1′ now means global/universal and a ’0′ is now for
local addresses. According to RFC 4291, the reasoning behind using a ’0′
for local is that it makes it easier for administrators to hand
configure non-global identifiers. So instead of having to configure
0200:0:0:1, 0200:0:0:2, etc, the administrator can simply configure
0:0:0:1 and 0:0:0:2 for non-global identifiers.

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]]> By: abcd http://blogs.cisco.com/security/ipv6-addressing/#comment-140242 abcd Thu, 31 Mar 2011 20:04:27 +0000 http://blogs.cisco.com/?p=23506#comment-140242 Hi,

I would like to ask a question regarding the modified EUI-64 address.

If you have a look at the MAC address it is 02:03:e8:00:65:10, i.e. the u-bit is set to “1″. As far as I know IEEE registration authority mentioned that if u bit is set to 0 it is a universally (globally) administered, i.e. it is globally unique address. If u bit==1 the address is locally administered and it is not guaranteed that this address is unique. Isn’t that true?

There must be a difference because IEEE 802 addresses have different meaning due to the value of u, don’t you agree?

Thanks,
abcd

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