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From: Owen DeLong <owen@delong.com> In-Reply-To: <BANLkTinmwCK8JMHRKaB-VOdn3FAG0YCtog@mail.gmail.com> Date: Thu, 7 Apr 2011 05:48:50 -0700 To: Vikas Sharma <vikassharmas@gmail.com> Cc: nanog@nanog.org Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org On Apr 7, 2011, at 1:18 AM, Vikas Sharma wrote: > Hi, >=20 > How to get link-local address from BIA. I have seen some information > on Internet but it is not working for all. >=20 Pretty simple: Split the BIA into two 24 bit chunks: cc000b / fc0000 Then insert fffe in the middle: cc000b fffe fc0000 Now invert the 0x02 bit of the first octet: ce000b fffe fc0000 Prefix with fe80:: fe80::ce00:0bff:fefc:0000 Which if you shorten it becomes: fe80::ce00:bff:fefc:0 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > The BIA in this case is cc00.0bfc.0000. The rules for the modified > EUI-64 addressing are: >=20 > =95FFFE 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 > =95Thereafter 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 > =95At last, change all points =91.=92 to colons =91:=92 and delete all = leading > zeros, then you got your link-local IPv6 address: > FE80::CE00:BFF:FEFC:0 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >=20 > So if your BIA is 0008.209a.081b (bia 0008.209a.081b), how link-local > be calculated. This is the link-local on router =3D> > IPv6 is enabled, link-local address is FE80::208:20FF:FE9A:81B >=20 > Also on XR below is the link local address >=20 > Loopback6 is Up, ipv6 protocol is Up, Vrfid is default (0x60000000) > IPv6 is enabled, link-local address is fe80::884c:2dff:fe84:8d75 >=20 > I can not see any interface with BIA ending with 75 ... >=20 Have you looked for the BIA on the loopback interface? While it's not a hardware interface, per se, the device is obviously assigning a BIA of 8a:4c:2d:84:8d:75 to the loopback6 interface. > Can someone explain me this? >=20 I think I just did. ;-) Owen
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