In SQL 2008 Setup, based on Server 2008 R2 you cannot select the public Interface in setup.
Maybe no Interface is displayed or only a few, but not this one you need for communication to the sql clients...
Cause:
Only Network Interfaces assigned with a default gateway are listed in the setup of the administrative interface.
solution:
Assign a default gateway on each interface you need to communicate with the clients.
if there is not always a possible gateway to use, walk to this configuration:
Assing for example a dummy gateway, such a domain controller who is not routing...
now, change all gateway entries into a manual metric.
The important gateway gots a metric of 1.
for example the dummy gateways got the lowest metric, in this configuation the 2.
Server cannot understand different gateways with a default metric.
the communication fails!
if you have to assign multiple gateways, you have to work with manuel merics, and this functions very well.