Hello!

I have two CAS/MB servers in my test lab - Exch1 and Exch2 (20.1.1.11 and 20.1.1.12 respectively) - and I was very surprised to see them "talking" to each other using their 6TO4 virtual adapters:

Q1: Is this behaviour normal for Exchange 2013SP1?

Q2: What if I disable 6TO4 adapter?

Thank you in advance,

Michael

• Edited by MF47 Wednesday, June 10, 2015 10:02 AM typo

"Disabling it should not break anything as such," - suppose once I disable IPv6 for the "main" network adapter (20.1.1.12) Exchange will try the next network adapter (either physical or virtual) with the IPv6 enabled.

Thank you once again,Satyajit!

Regards,

Michael

Hi,

First of all, we need to know more about 6to4 adapter. 6to4 is an address assignment and router-to-router, host-to-router, and router-to-host automatic tunneling technology that is used to provide unicast IPv6 connectivity between IPv6 sites and hosts across the IPv4 Internet. 6to4 treats the entire IPv4 Internet as a single link.

For example, your CAS server is configured from a public range IPv4 address 20.1.1.11 as shown in the IPCONFIG output. Assume IPv6 is also enabled and there is no global IPv6 address explicitly configured in your server. The default behavior in Windows is to generate 6to4 tunnel address and in this case is configured in the 6to4 Adapter section of IPCONFIG output.

The 6to4 tunnel address always starts with a 2002. The remaining digits 1401:10C are generated based out of the IPv4 address that is configured on your server and it gets repeated in the interface ID portion also. It is basically hex representation of IPv4 address values. If you convert the decimal digit 20 to a hex value, it is 14, 1 becomes 01 in hex and so on.

If you want to know more about how the tunneling technologies work, review the white paper in this TechNet link

https://technet.microsoft.com/en-us/library/bb726951.aspx

So enabling or disabling the 6to4 adapter is depending on your preferences.

More information about 6to4 adapter, you can refer to this blog.

http://blogs.technet.com/b/askpfeplat/archive/2013/11/18/ipv6-for-the-windows-administrator-the-2002-6to4-tunnel-address-and-its-impact.aspx

Best Regards.

"Assume IPv6 is also enabled and there is no global IPv6 address explicitly configured in your server." - you mean I have my physical Nic's IPV6 disabled?

"The default behavior in Windows is to generate 6to4 tunnel address and in this case is configured in the 6to4 Adapter section of IPCONFIG output." - but the question is should Exchange use this virtual adapter instead of 20.1.1.12?

Hi MF47,

6TO4 adapter is a tcpipv6 component, hence disabling IPv6 should involve disabling that as well.

Now regarding the mail flow part, I would guess it doesn't use IPv6. But if we see the statement from MS

"Because Windows was designed specifically with IPv6 present, Microsoft does not perform any testing to determine the effects of disabling IPv6."

They are saying that both IPv4,IPv6 are required for Exchange to work as they have not tested disabling them. Hence is all upto your findings that will it impact or not.

References:

IPV6 Addresses for Exchange server appearing in domain DNS even with IPV6 disable on Exchange server

Forwarding on the 6to4 network interface cannot be enabled

http://blogs.technet.com/b/edgeaccessblog/archive/2011/01/28/forwarding-on-the-6to4-network-interface-cannot-be-enabled.aspx