<p>I need to do a join across two different database servers (IPs 10.0.0.50 and 10.0.0.51). What's the best way?</p>

You need to use sp_linkedserver to create a linked server.
```
```
sp_addlinkedserver [ @server= ] 'server' [ , [ @srvproduct= ] 'product_name' ] 
 [ , [ @provider= ] 'provider_name' ]
 [ , [ @datasrc= ] 'data_source' ] 
 [ , [ @location= ] 'location' ] 
 [ , [ @provstr= ] 'provider_string' ] 
 [ , [ @catalog= ] 'catalog' ]
```
```
More information available on
MSDN
.