here's the reply from support:
If Updatemanager is binding the wrong nic you have two possible workarounds.
The preferred method is to edit the Update Manager configuration file, located on the Update Manager Server.
1.Launch the windows service management console and stop VMware Update Manager Service.
+ Start -> Run -> type 'services.msc' -> press 'Enter'.+
2.Edit the Update Manager configuration file.
+ Note: the default location is C:\Program Files\VMware\Infrastructure\Update Manager\vci-integrity.xml file. Change the drive letter and/or path as required.+
3.Locate the section named "HostConfig". It should look something like this:
+ <HostConfig>+
+ <PatchDepotUrl></PatchDepotUrl>+
+ Note: Update Manager ignores the information about the hostname during installation and leaves this section empty. That causes the Update Manager to use the first NIC in the binding order on the Windows machine that runs VirtualCenter and Update Manager.+
4.If your VirtualCenter hostname is for example "vcServer", enter the address as noted below:
+ <HostConfig>+
+ <PatchDepotUrl>http://vcserver/vci/hostupdates/hostupdate</PatchDepotUrl>+
+ Note: This VirtualCenter host name should be pingable from your ESX Server hosts.+
5.Save and exit the configuration file.
6.Restart VMware Update Manager from the service management console.
Alternatively, you can change the binding order of the network adapters on the machine running VMware Update Manager.
1.Open the Network Connections control panel.
+ Start -> Run -> type 'ncpa.cpl' -> press 'Enter'.+
2.You can see the available connections in the LAN and High-Speed Internet section of the Network Connections window.
3.From the Advanced menu, select Advanced Settings.
4.Select the Adapters and Bindings tab.
5.In the Connections area, select the connection you wish to move higher in the list and use the arrow buttons to move the connection.
Note: Place the NIC that is accessible by ESX server as the first NIC in the list.
Note:
* The Adapters and Bindings tab lists the connections in the order in which the connections are accessed by network services. The order of these connections reflects the order in which TCP/IP or the next available protocol is bound to the network adapters. The bindings for remote access connections apply to all remote access connections.
* The Provider Order tab lists the network providers for this computer. You can use the arrow buttons to change the order in which these providers are accessed. You can arrange the order in which the computer accesses information about the network. Providers and other connections are accessed in the order in which the providers and the connections are listed.