Same nic/hardware address, different link-local addresses

[kriteknetworks]

Hi folks, came across this today, dual boot machine Windows 7/Fedora 14, each OS displays the link-local address differently for the same nic, is this normal?

Fedora 14:
eth0      Link encap:Ethernet  HWaddr 00:1E:C9:40:F5:AD
          inet addr:192.168.1.50  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: 2001:470:8:12:21e:c9ff:fe40:f5ad/64 Scope:Global
          inet6 addr: fe80::21e:c9ff:fe40:f5ad/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:200 errors:0 dropped:0 overruns:0 frame:0
          TX packets:203 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:32065 (31.3 KiB)  TX bytes:23127 (22.5 KiB)
          Interrupt:16

Windows 7:
Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . : int.kritek.net
   Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit Controller
   Physical Address. . . . . . . . . : 00-1E-C9-40-F5-AD
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : 2001:470:8:12:9000::200(Preferred)
   Lease Obtained. . . . . . . . . . : Monday, February 28, 2011 11:03:42 AM
   Lease Expires . . . . . . . . . . : Monday, February 28, 2011 11:31:21 AM
   Link-local IPv6 Address . . . . . : fe80::c565:84fc:ae12:b1b8%11(Preferred)
   IPv4 Address. . . . . . . . . . . : 192.168.1.50(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : Monday, February 28, 2011 11:03:44 AM
   Lease Expires . . . . . . . . . . : Monday, February 28, 2011 1:03:44 PM
   Default Gateway . . . . . . . . . : fe80::220:35ff:fee7:d976%11
                                       192.168.1.4
   DHCP Server . . . . . . . . . . . : 192.168.1.1
   DHCPv6 IAID . . . . . . . . . . . : 234888905
   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-14-FC-65-E0-00-1E-C9-40-F5-AD
   DNS Servers . . . . . . . . . . . : 2001:470:e006:2b::1
                                       192.168.20.2
   Primary WINS Server . . . . . . . : 192.168.1.1
   NetBIOS over Tcpip. . . . . . . . : Enabled

[Mierdin]

This has to do with the way Windows generates link local addresses. Typically a linux system will use the commonly recognized EUI-64 format for the last 64 bits of the address (easily recognized by the fffe in the middle), but windows has the ability to make it completely random. Obviously heavily tied to DAD to prevent dupes.

Read here for more info: http://technet.microsoft.com/en-us/magazine/2007.08.cableguy.aspx

[antillie]

If you want Windows to use the EUI-64 format address instead of the random one you can make it do so with the following commands:

netsh interface ipv6 set global randomizeidentifiers=disabled
netsh interface ipv6 set privacy state=disable

[brinkers]

shouldn't fedora be avoiding using  EUI-64?   isn't that what Privacy Extensions for Stateless Address Autoconfiguration in IPv6 rfc is all about?

just trying to understand stuff :-)

[cholzhauer]

shouldn't fedora be avoiding using  EUI-64?   isn't that what Privacy Extensions for Stateless Address Autoconfiguration in IPv6 rfc is all about?

just trying to understand stuff :-)

Depends what the setting is.  It seems like Linux has the privacy extensions turned off by default and Windows has them turned on by default.