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I have automatically configured IPv6 address on my Mac OS X 10.6:

$ ifconfig
ether 00:16:cb:94:1a:79 
inet6 fe80::216:cbff:fe94:1a79%en0 prefixlen 64 scopeid 0x4 
inet netmask 0xfffffe00 broadcast
media: autoselect (100baseTX <full-duplex,flow-control>)
status: active


$ sysctl -a
net.inet6.ip6.use_tempaddr: 1

(I don't know is it necessary)

But after I reconfigure the IPv6 address on Preference Pane (Networking) nothing changed. How could I change my IPv6 address?


I have select FEE2:f68::1986:69af address. The reason I do this to prevent adding the %en0 to the address string.

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You will always have a link local address according to the RFCs, but if you specify an address in Preferences, it should show up. – Sep 9 '11 at 9:33
I have updated my question – user83293 Sep 9 '11 at 10:01
up vote 0 down vote accepted

With IPv6 you always have a link-local address (those that usually start with fe80:, although all addresses in the range fe80:0000:0000:0000:0000:0000:0000:0000 - febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff are link-local). The address you configure in the Preferences pane should show up on the interface. Configure a global IPv6 address on the interface, or if you don't have a global prefix then use ULA. The prefix length for a LAN is always /64, unless you really know what you are doing :-)

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Oh, and the net.inet6.ip6.use_tempaddr: 1 is for when you don't manually configure your IPv6 address. Then it randomly generates its own address based on the information in the Router Advertisement (assuming you have a router on your network) – Sander Steffann Sep 9 '11 at 10:12
Just to say that the correct prefix of a link-local address is fe80::/64 as specified in RFC4291. – Sep 11 '11 at 0:18
No it is not. The official prefix for link-local is fe80::/10, but yes: RFC4291 describes how the bits should be used. At the start of section 2.4 it specifies fe80::/10 though, and not a /64. – Sander Steffann Sep 12 '11 at 6:05

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