A more specific name for this is link-local addressing. These addresses only speak to other devices on the same switch or LAN that have also autoconfigured themselves, but they cannot speak across routers to the rest of the networked world. IPv6 devices always create a link-local address that will only speak to other devices on the same switch or LAN, whether or not another address is assigned. IPv6 link-local addresses are in the fe80:/10 prefix, meaning they will begin with fe8, fe9, fea or feb. Let’s take a look:

Windows IP Configuration

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . : ad.itkia.com
   IPv6 Address. . . . . . . . . . . : 2001:db8:192:0:6470:6fb9:76c7:aa85
   Link-local IPv6 Address . . . . . : fe80::6470:6fb9:76c7:aa85%11
   IPv4 Address. . . . . . . . . . . : 192.168.1.56
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : fe80::214:d1ff:fe1a:a533%11
                                       192.168.1.1

I highlighted in red the link-local addresses in the “ipconfig” output. Note that the gateway is a link-local address instead of the router’s public address. The link-local address for my machine is the first one highlighted.

But what is that “%11″ at the end? Remember, these are link-local addresses, and there is no concept of routing to other networks. Your computer may have or think it has more than one link. If you try using a link-local address and get an error, add the “%11″ to the address to tell Windows which link to use. This is the Scope ID and tells Windows which link to look on for specified link-local address. It isn’t really part of IPv6 itself, and the Scope ID never enters the packet or the network.

When I first started playing with IPv6 I tried pinging and accessing web sites on my local LAN using the link-local addresses, and it wasn’t working. (It’s working fine now, so I can’t demonstrate failure.) I had to add the %n Scope ID, and then it worked for me. Expect to encounter this issue if you are pinging link-local addresses from a multihomed host.

If you have public or even private IPv6 addresses you can just ignore the link-local addresses. They are used by IPv6 extensively for autoconfiguration, multicasting and neighbor discovery, but they aren’t meant to be used by applications or users, and they should never have names resolving to them.

I am seeing a lot of searches for “arp -a” “IPv6″. So, you want to know how to perform “arp -a” in IPv6? Well, I’ll show you. The equivalent of ARP (Address Resolution Protocol) in IPv6 is NDP (Neighbor Discovery Protocol), although there is no “ndp” command. Sadly, you have to type more.

Windows netsh command “netsh interface ipv6 show neighbors”:

C:\>netsh int ipv6 show neigh

Interface 11: Local Area Connection

Internet Address                              Physical Address   Type
--------------------------------------------  -----------------  -----------
2001:db8:192::224                             00-14-d1-1a-a5-33  Stale (Router)
2001:db8:192:0:ad:8b35:7475:d1eb              00-00-00-00-00-00  Unreachable
2001:db8:192:0:897:65a5:2a77:2b78             00-00-00-00-00-00  Unreachable
2001:db8:192:0:3889:8f1:bfc9:29c1             00-11-d8-6e-1c-6d  Stale
2001:db8:192:0:412b:1a9e:1186:3569            00-00-00-00-00-00  Unreachable
2001:db8:192:0:845c:cc6d:e8ec:4c11            00-14-d1-1a-a5-fd  Reachable
2001:db8:192:0:f504:2282:bce7:a986            00-00-00-00-00-00  Unreachable
fe80::ad:8b35:7475:d1eb                       00-00-00-00-00-00  Unreachable
fe80::214:d1ff:fe1a:a533                      00-14-d1-1a-a5-33  Reachable (Router)
fe80::412b:1a9e:1186:3569                     00-14-d1-1a-a4-9e  Stale
ff02::2                                       33-33-00-00-00-02  Permanent
ff02::c                                       33-33-00-00-00-0c  Permanent
ff02::16                                      33-33-00-00-00-16  Permanent
ff02::1:3                                     33-33-00-01-00-03  Permanent

You may notice some duplicate and unreachable physical (MAC)  addresses. The unreachables are due to privacy addresses. My Windows boxes by default use temporary IPv6 addresses than change periodically to attempt some measure of privacy. I think this is dumb, and it can be turned off by “netsh interface ipv6 set privacy state=disabled” on each machine. The duplicates are because each MAC has multiple IPv6 address scopes. Most machines will have the public IPv6 address and a link-local IPv6 address, usually starting with fe80.

I will also draw your attention to the fact that the physical MAC address is transliterated and somewhat recognizable in the internet address for link local addresses and most non-private addresses. Current Ethernet MAC’s are 48-bit addresses. IPv6 is geared for 64-bit unique identifiers, and there is a standard conversion to represent MACs as EIU-64 addresses.

The ff02: addresses are multicast addresses. In IPv6 there is no broadcast, but there are various multicast scopes to address the link-local domain, the site-local domain and other domains.

The Linux command:

$ ip -6 neigh show
fe80::6470:6fb9:76c7:aa85 dev eth1 lladdr 00:21:9b:16:a0:42 STALE
2001:db8:192:0:6470:6fb9:76c7:aa85 dev eth1 lladdr 00:21:9b:16:a0:42 REACHABLE
fe80::3889:8f1:bfc9:29c1 dev eth1 lladdr 00:11:d8:6e:1c:6d REACHABLE
2001:db8:192:0:845c:cc6d:e8ec:4c11 dev eth1 lladdr 00:14:d1:1a:a5:fd REACHABLE
2001:db8:192:0:ad:8b35:7475:d1eb dev eth1 lladdr 00:1e:90:70:9c:17 STALE

The “ip” command is /sbin/ip which is part of the iproute package in most distributions.

Then about a month ago I performed a laptop refresh for an industrial company where the new laptop was a Configuration Manager (SMS)-managed Vista Business operating system. This was actually problematic, but the issues were due to client network latency between the laptop and the software distribution point, not to Vista itself .

Today I saw Server 2008 in production at a big box retailer while testing a newly installed KVM, and I made an appointment for this week to refresh a laptop user at at IT services firm to a new managed laptop running Windows 7 64-bit. I’m speaking about real, managed deployments here, not a lab machine or a rogue user installing his own software. Color me impressed.

I don’t think this is simply coincidental to the upswing in adopting Windows Deployment Services that I’ve seen over the past two years. Before two years ago, all client images I dealt with were Ghost, Altiris or various Linux-based imaging software, but then I noticed more and more clients using WDS for their newer hardware deployments. Now I have several clients using DVD, PXE and flash boot to image their systems with WDS. And once you have that infrastructure in place, imaging Vista or Windows 7 is as easy as Windows XP. And now apparently patch and application management for Vista, Win7 and Server 2008 is deployed more widely in the enterprise. Welcome to the present!

I recently set up Windows Live Mail to read my Google Mail account, and I was periodically getting the “new mail” sound without getting any new mail. I discovered that Windows Live Mail was syncing the Spam folder and notifying me every time there was new spam. Oops. So I right-clicked on the Spam folder—subfolder of [Gmail]—highlighted “Synchronization Settings” and selected “Don’t Synchronize”.

I may have to do this with other folders as any new mail with multiple labels will show up in an IMAP folder for each label. I haven’t noticed yet, but I’m guessing Windows Live Mail will then tell me there’s a new message for each label it has.

A client was getting blue screen errors with STOP 0×0000007E. This indicates drivers or hardware, and given that the machines were fine until upgrading to WinXP SP2 I decided it must be a driver.

Through trial and error I found that Logitech Mouseware 9.76 was installed on the PCs and was causing sporadic blue screens when a USB mouse was connected. Just uninstall Mouseware, let Windows XP install the native driver and all is well.

UPDATE: It has come to my attention that this problem may be related to DeviceLock USB security program installed on my client’s computers. It’s possible that Mouseware and SP2 alone won’t cause the blue screen crashes but that Mouseware and DeviceLock are conflicting.