Windows 7: Two systems: why is one using IPv4, the other IPv6?

I installed Windows 7 on two computers this week here at home. They are both connected to the same NAT router (which connects me to my DSL connection), so this is a VERY conventional setup.

IPconfig shows, that both systems have an IPv4 as well as IPv6 running, both consequently also have two addresses (an IPv4 as well as an IPv6 address), though the connection to the internet is IPv4 only.

Now I just noticed, that if I ping computer 1 from computer 2 the name resolves to an IPv4 address (192.168.1.12). If I ping in the other direction the name is resolved to an IPv6 address (fe80::281a:b9de:5543:3b62%11). I have installed both systems from the very same CD and I didn't do anything special nor different regarding networking. So why is one PC resolving system names using IPv6, the other IPv4?

In principle I couldn't care less which IP version the systems are using as long as connections work ok, but I am using a file synchronization utility that apparently compares addresses and if the subnets of the two system don't match switches to a mode where it synchronizes via a proxy out somewhere in the network.
If it detects, that both systems are in the same subnet, they connect directly which then runs much, much faster. That's why I need both system to use the same subnet and hence they should both use the same default IP stack.

Can one change the preference or order of these stacks?

Michael

Hi.

Not sure why it's doing that. Did you install a 3rd party firewall on one and not the other?

If you're using static ip addresses, you can place entries for each machine on the network in the hosts file.

C:\Windows\System32\drivers\etc\hosts

Open it with notepad. It's basically the system's first dns server.

Or you can test ping like this:

ping -4 hostname

ping ipaddresshere

Michael

Its is actually easy. Homegroup uses IPv6, workgroup uses ipv4. If you were to change from homegroup to workgroup it would have no choice but to use the same IPv4. PLus you can disable IPv6 just to be sure. Same subnet, same router.

Hope it helps

Ken J+

In principle you will have to decide which internal address you want to sync both machines, as ken has suggested both machines from within the LAN will need identical address. Another issue will be "Port Triggering" AKA Port forwarding. With the routers native firewall its designed not to let traffic in.

Workgroup does not force IPv4! Nor is the problem Homegroup or Workgroup, the problem is one machine is referencing the other using a different IP scheme. This can be due to several reasons. First-in-first-out comes to mind. When doing a lookup on the machine name it looks for the first entry that it finds, could be an IPv4 or IPv6 address. To avoid this wildcard lookup, you can either force one address scheme over another. (Normally offered in software...ping for example offers -4 and -6 switches)

You can try this option, in the Advance settings for either IPv4 or IPv6, go to the DNS tab and toggle "Register this connection's addresses in DNS" on or off.

A Workgroup setup works independent of the IP address scheme, why else do you think Windows Vista can use Workgroups in an IPv6 environment?