Managed switches — These switches have one or more ways, or interfaces, to modify the operation of the switch. Common management methods include: a serial console or Command Line Interface accessed via telnet or Secure Shell; an embedded Simple Network Management Protocol SNMP agent allowing management from a remote console or management station; a web interface for management from a web browser. Examples of configuration changes that one can do from a managed switch include: enable features such as Spanning Tree Protocol; set port speed; create or modify VLANs, etc.
Two sub-classes of managed switches are marketed today:
Smart (or intelligent) switches — These are managed switches with a limited set of management features. Likewise “web-managed” switches are switches which fall in a market niche between unmanaged and managed. For a price much lower than a fully managed switch they provide a web interface (and usually no CLI access) and allow configuration of basic settings, such as VLANs, port-speed and duplex.
Enterprise Managed (or fully managed) switches – These have a full set of management features, including Command Line Interface, SNMP agent, and web interface. They may have additional features to manipulate configurations, such as the ability to display, modify, backup and restore configurations. Compared with smart switches, enterprise switches have more features that can be customized or optimized, and are generally more expensive than “smart” switches. Enterprise switches are typically found in networks with larger number of switches and connections, where centralized management is a significant savings in administrative time and effort. A Stackable switch is a version of enterprise-managed switch.
Most managed switches offer you features like:
- View the bridging table to see which MAC addresses are associated with a given port
- View error statistics for each port
- View packet transmit / receive statistics for each port
- Set duplex / speed negotiation (or lack thereof) on a per-port basis
- View power-over-Ethernet status and current draw for each port (if applicable)
Typically there is a TELNET, serial, and / or web-based interface to interact with the switch.
Many managed switches allow you to poll the device with the SNMP protocol to use the information described above in graphs, alerts, etc. (Beware– some low end managed switches, like the Dell 27xx series, don’t have SNMP functionality!)
Most managed switches today support things like 802.1D spanning tree, 802.1q VLANs, and 802.3ad link aggregation, and the management interface allows you to configure these various features. You can typically setup port VLAN memberships, link aggregation groups, and control spanning tree parameters all from a web or command-line interface.
A goodly number of managed switches have taken to emulating the Cisco command-line interface (HP ProCurve, Dell PowerConnect to name a couple) such that someone with Cisco-specific knowledge can easily configure those switches.