Tonight I was deploying an OVF on a newly upgraded vCenter version 6.0U1 through the vSphere Web Client. This is the Windows server (VCS), not the appliance (VCSA). I ran into this wonderful error while deploying an OVF on the storage selection step:

There is KB 2053229 that says this was resolved in vCenter 5.1U2. However, the underlying issue is that the client attempts to communicate with the vCenter service in a new session to validate the storage and so the problem may remain in certain environments. I found that a teredo tunneling address was being used during storage selection rather than the IPv4 address that I connected to in my web browser. These addresses are provided for “free” with Windows Server 2008R2. The (magic?) design of teredo is that it should not be used when an IPv4 A record exists and should only be used for IPv6 URLs. I’m not sure why VCS would use this, just that I observed it being used. I discovered this with the help of two artifacts: 1) another node on a remote network was able to make it past storage selection; and 2) I saw a deny entry in syslog with my problematic management node to the VCS’s IPv4 addresses with IPv6 as the service:

The KB article points to DNS, so I checked and found a AAAA record for vCenter. Delete that record, wait for it to replicate throughout Active Directory and expire, and reload the vSphere Web Client. You should no longer see a log failure for IPv6 and your OVF deploy should at least make it past the storage selection stage. I hope this helps!