What’s the difference between a hub, an unmanaged switch and a managed switch?

Hubs transmit all data out all connected ports.  Switches automatically learn the network layout and then only transmit data where it needs to go, making the network more efficient.  Managed switches add an additional level of configuration and monitoring capability to a network.

Ethernet networks are created with many point-to point connections, and infrastructure devices such as hubs and switches are used to connect the devices.

There is often some confusion between Ethernet switches and hubs.  Hubs essentially act like an “extension cord” on the network.  All incoming messages are retransmitted out the ports to every device.  Each device sees messages for all other devices, regardless of the intended destination.  The unnecessary traffic can slow the network and cause widely varying response times (nondeterministic) due to message collisions. 

Ethernet switches, both unmanaged and managed, avoid collisions by routing messages to only the intended devices. When a switch receives an Ethernet message (packet),  it reads the address of the device for which the message is intended, and then transmits the message out of only the port to which that device is connected (even if it is connected through several other switches). 

Unmanaged switches are the lowest cost and provide this basic switching functionality.  They do not need an IP address, and do not feature web page or SNMP management or any other advanced functions.

Managed switches have built-in web pages that can be accessed by a standard web browser for custom configuration. In addition, managed switches offer IT compatibility for configuration and monitoring via SNMP (Simple Network Management Protocol) and support Rapid Spanning Tree Protocol (RSTP) to allow creation of robust redundant and self-healing network connections between corporate networks and the factory floor.  Of particular importance to applications like Ethernet/IP, support for IGMP Snooping & Query protocols provide multicast filtering to avoid end device overload.  In addition to these managed functions, some managed switches also provide support for additional managed features such as Fast Ring high-speed redundancy, VLAN, Port Security, etc.

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