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why use prefixlen 128 on Mac while IPv6 Address from HE has prefixlen 64?

Started by sleepingdust, August 26, 2013, 08:10:10 AM

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This might be a complete amateur question:

My IPv6 address assigned by HE is something like 2001:470:20:5c2::2/64

If I understand this correctly, the number after the oblique (/) is the prefix length, then why the tunnel tutorial Configuring a tunnel under *BSD & MacOS X uses prefix length 128 for Mac?

Should it be:
ifconfig gif0 inet6 $ipv6b $ipv6a prefixlen /64
instead of
ifconfig gif0 inet6 $ipv6b $ipv6a prefixlen /128



IIRC that was a change in newer versions of OSx (someone please correct me if I'm wrong) and the tutorial was obviously written before the new versions were released.


But why ifconfig gif0 still show the prefixlen 128 when I configured it with prefixlen 64?

gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
tunnel inet -->
inet6 fe80::21b:XXXX:fe93:eee%gif0 prefixlen 64 scopeid 0x2
inet6 2001:470:18:XXX::2 --> 2001:470:18:XXX::1 prefixlen 128