pi@raspberrypi:~ $ iobroker setup custom
Current configuration:
- Objects database:
  - Type: file
  - Host/Unix Socket: 0.0.0.0
  - Port: 9001
- States database:
  - Type: redis
  - Host/Unix Socket: 0.0.0.0
  - Port: 6379
- Data Directory: ../../iobroker-data/

Type of objects DB [(f)ile, (r)edis], default [file]: f
Host / Unix Socket of objects DB(file), default[0.0.0.0]:
Port of objects DB(file), default[9001]:
Type of states DB [(f)file, (r)edis], default [redis]: r
Host / Unix Socket of states DB (redis), default[0.0.0.0]: 0.0.0.0
Port of states DB (redis), default[6379]:
Host name of this machine [raspberrypi]:
updating conf/iobroker.json
pi@raspberrypi:~ $ iobroker multihost enable
Please check the binding of redis service. By default it is only local: http://download.redis.io/redis-stable/redis.conf
Change "bind 127.0.0.1" to "bind 0.0.0.0" or to others.
No configuration change needed.


Multihost discovery server: enabled
Discovery authentication:   enabled
Objects:                    file on 0.0.0.0
States:                     redis on 0.0.0.0

Der Slave so:

pi@brokerslave:~ $ sudo iobroker setup custom
Current configuration:
- Objects database:
  - Type: file
  - Host/Unix Socket: 192.168.178.49
  - Port: 9001
- States database:
  - Type: redis
  - Host/Unix Socket: 192.168.178.49
  - Port: 6379
- Data Directory: ../../iobroker-data/

Type of objects DB [(f)ile, (r)edis], default [file]: f
Host / Unix Socket of objects DB(file), default[192.168.178.49]:
Port of objects DB(file), default[9001]:
Type of states DB [(f)file, (r)edis], default [redis]:
Host / Unix Socket of states DB (redis), default[192.168.178.49]:
Port of states DB (redis), default[6379]:
Host name of this machine [brokerslave]:
updating conf/iobroker.json
pi@brokerslave:~ $ iobroker multihost connect
No connection to states 192.168.178.49:6379[redis]

Warum verbindet der slave nicht auf den master?

[Edit:] Hat sich erledigt, ich musste in der redis.conf noch bind setzen.