Management of a Cisco switch ( or most other vendor switches) can be done using CLI or web interface. Your switch in Perth and switch in Sydney need to be configured with an ip address (obviously two different subnets) and also a default gateway. If there is no default gateway configured on both switches, management of one switch from the other network is not possible.
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus