As you have seen in the screenshots, the master poller has its hostname set to localhost as well. While this does not have any negative effect on the functionality of the remote poller, it has an impact on setting up devices or using functionality like the real-time feature for viewing graphs.
For devices being polled from a remote poller, the master server will ask that remote poller to provide the required data. The remote poller then gathers the data and provides it to the master server using the hostname from the Data collectors table, which is still set to localhost. Obviously, the remote poller will therefore not be able to provide the data to the master server unless you change the hostname to the correct resolvable hostname as well.
