link-local address calculation

Vikas Sharma vikassharmas at gmail.com
Thu Apr 7 03:18:33 CDT 2011


Hi,

How to get link-local address from BIA. I have seen some information
on Internet but it is not working for all.

=============
The BIA in this case is cc00.0bfc.0000. The rules for the modified
EUI-64 addressing are:

•FFFE will be put in between the vendor-id (3 most significant bytes)
and the extension-id (3 least significant bytes), which will lead to
cc00.0bFF.FEfc.0000
•Thereafter the seventh bit, known as universal/local bit, gets
inverted. So first change the cc00 from hex to binary, which leads to
110011 0 000000000 and then invert the seventh bit (here a 0): 110011
1 000000000. Moved back to hex this will give CE00
•At last, change all points ‘.’ to colons ‘:’ and delete all leading
zeros, then you got your link-local IPv6 address:
FE80::CE00:BFF:FEFC:0
============

So if your BIA is 0008.209a.081b (bia 0008.209a.081b), how link-local
be calculated. This is the link-local on router =>
  IPv6 is enabled, link-local address is FE80::208:20FF:FE9A:81B

Also on XR below is the link local address

Loopback6 is Up, ipv6 protocol is Up, Vrfid is default (0x60000000)
  IPv6 is enabled, link-local address is fe80::884c:2dff:fe84:8d75

I can not see any interface with BIA ending with 75 ...

Can someone explain me this?

Regards,
Vikas




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