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This chapter introduces the Catalyst 2820 series Ethernet switches, also referred to as the Catalyst 2820 switches, and covers the following topics:
The Catalyst 2820 series Ethernet switches provide 25 10-Mbps switched Ethernet connections: 24 10-Mbps connections to 10BaseT-compatible devices (such as single workstations and 10BaseT hubs) and one 10-Mbps connection to an AUI. Switches with the optional Catalyst 2820 modules installed can provide 100BaseT, FDDI, and ATM connectivity to servers and backbones.
The Catalyst 2820 series consists of the following switches:
Each Catalyst 2820 switch, as represented in the following illustration, provides the key features in Table 1-1. 
| Feature | Description |
|---|---|
| Performance and Configuration |
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| Management |
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| Power Redundancy |
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The front panel of a Catalyst 2820 switch provides 24 switched 10BaseT ports, 2 expansion slots, LEDs, and a Mode button.
The 24 switched 10-Mbps ports (1x through 24x) use standard RJ-45 connectors
(Figure 1-1). These fixed ports can connect to 10BaseT-compatible devices, such as individual workstations and hubs, with Category 3, 4, or 5 unshielded twisted-pair (UTP) cabling. For information on connecting to these ports, see the "Connecting to the Switched 10BaseT Ports" section.
The two expansion slots are for the optional Catalyst 2820 100BaseTX, 100BaseFX, FDDI, and Asynchronous Transfer Mode (ATM) modules. The module ports can connect to backbones, servers, switches, and routers with Category 5 UTP or fiber-optic cabling. For more information about these modules, refer to the Catalyst 2820 Modules User Guide and the Catalyst 2820 ATM Modules Installation and Configuration Guide.
You can use the LEDs to monitor network activity and switch performance. The Mode button is used to select the modes in which the port status LEDs operate (Figure 1-2).
The colors of the redundant power system (RPS) LED reflect the RPS status (Table 1-2).
| Color | RPS Status |
|---|---|
Off | Power is OK (internal power supply is powered up). |
Solid green | Power is OK (RPS is powered up and operational). |
Solid amber | RPS is not operational or is not connected properly. |
Flashing amber | RPS indicates the internal power supply and RPS are powered up, and that the internal power supply is powering the switch. |
The colors of the system status (SYSTEM) LED show if the switch is receiving power and functioning properly (Table 1-3).
| Color | System Status |
|---|---|
Off | Switch is not powered up. |
Solid green | Switch is operating normally. |
Solid amber | Switch is receiving power but might not be functioning properly. One or more power-on self-test (POST) errors occurred. The Menu Console Logon Screen message identifies which nonfatal test(s) failed. Note No message is displayed if a fatal error occurs. |
The colors of the expansion slot status (A and B) LED reflect the status of an installed module (Table 1-4).
| Color | Expansion Slot Status |
|---|---|
Off | No module is in the slot, or the module has not been identified by the system and is not operational. |
Solid green | Module is operational. |
Flashing green | Module is running POST. |
Solid amber | Module failed POST and is not operational. |
The port mode LED reflects the mode you selected with the Mode button. To change the mode being displayed by a port status LED, press the Mode button to highlight the modes: STAT (port status), UTL (bandwidth utilization), and FDUP (full-duplex mode). After you release the Mode button, the selected mode remains on for 30 seconds before returning to the default mode.
The colors of the port status LEDs in STAT mode reflect the status of the individual ports (Table 1-5).
| Color | Port Status |
|---|---|
Off | No link. |
Solid green | Link operational (with no activity). |
Flashing green | Link operational (with activity). |
Alternating green and amber | Link fault. Error frames can affect connectivity. Excessive collisions, CRC errors, and alignment and jabber errors are monitored for a link-fault indication. |
Solid amber | Port is not forwarding. This could be because the port was disabled by management, suspended due to an address violation, or suspended by Spanning-Tree Protocol due to network loops. |
The colors of the port status LEDs in UTL mode reflect the current and peak bandwidth utilization of the switch (Table 1-6). Current bandwidth utilization is shown with a series of lit port status LEDs ending with a rapidly blinking one. Peak bandwidth utilization is indicated by the right-most solidly lit LED.
The peak utilization is recorded in the bandwidth-capture interval, described in the "Bandwidth Usage Report" section.
| Port Status LEDs | Mbps Activity |
|---|---|
1 to 8 | 0.1 to < 6 |
9 to 16 | 6 to < 120 |
17 to 24 | above 120 |
The colors of the port status LEDs in FDUP mode reflect which 10BaseT ports are operating in full-duplex mode (Table 1-7). (Modules supporting full-duplex operation have a resident LED to indicate full-duplex status.)
| Color | Full-Duplex |
|---|---|
Off | Half-duplex mode is operational. |
Solid green | Full-duplex mode is operational. |
The rear panel of a Catalyst 2820 switch has an AC power connection, an RJ-45 console port, a redundant power system (RPS) connection, and a switched Ethernet AUI port
(see Figure 1-3).
You can configure and manage the switch through the menu-based management console. Connect the console port to a management station or modem with the supplied RJ-45-to-RJ-45 rollover cable and adapters. For additional information, see the "Connecting to the Console Port" section.
You can connect the switched Ethernet AUI port to an Ethernet transceiver, which is then connected to a 10-Mbps Ethernet device through thick coaxial, thin coaxial, fiber-optic, or UTP cable. For additional information on connecting to this port, see the "Connecting to the Switched Ethernet AUI Port" section.
You can power the switch with the internal power supply and/or the Cisco 600W AC redundant power system (RPS). If you have the internal power supply and the RPS powered up at the same time, the RPS LED flashes amber. In this configuration, the internal power supply is powering the switch and the RPS will power the switch if the internal power supply fails.
To use the internal power supply, an autoranging unit supporting input voltages of
100 to 127/200 to 240 VAC, connect the supplied AC power cord to the AC power connection and to an AC power outlet.
For complete information about the RPS, see the Cisco RPS documentation.
 | Warning Attach only the Cisco RPS (model PWR600-AC-RPS) to the RPS receptacle. |
This section provides example configurations of networks using Catalyst 2820 switches:
In Figure 1-4, a Catalyst 2820 switch supports up to 25 switched (dedicated) Ethernet connections to workstations or 10BaseT hubs. Each workstation or hub directly connected to a switch port has a dedicated bandwidth of 10 Mbps. However, the workstations connected to the 10BaseT hub or repeater share the available 10 Mbps of bandwidth available.
You can connect Catalyst 2820 switches to servers and other switches through the Catalyst 2820 FDDI, ATM, 100BaseTX, and 100BaseFX switch modules. In Figure 1-5, three Catalyst 2820 switches connect to each other and to servers through the Catalyst 2820 single-port 100BaseT switch modules. If the module ports are configured for full-duplex operation, they provide a total of 200 Mbps of bandwidth on each port. Switched 10BaseT ports configured for full-duplex operation provide 20 Mbps of bandwidth to end stations.
You can create a 100-Mbps or ATM collapsed backbone by connecting Catalyst 2820 switches to a 100BaseT backbone switch or router, as shown in Figure 1-6. Two Catalyst 2820 switches connect to a Catalyst 5000 series switch, a LightStream 1010 switch, or a Cisco 7000 series router through the Catalyst 2820 ATM module or Catalyst 2820 single-port 100BaseT switch module. In CollisionFree full-duplex mode, 200 Mbps of bandwidth is available to both Catalyst 2820 switches. The distance between each Catalyst 2820 switch and the backbone switch or router can be increased to
2 kilometers by using the Catalyst 2820 single-port 100BaseFX switch module in full-duplex mode with fiber-optic cabling.
You can create a 100-Mbps or ATM redundant backbone network by connecting Catalyst 2820 switches to 100BaseT or ATM backbone switches or routers, as shown in Figure 1-7. Each Catalyst 2820 switch connects to the two Catalyst 5000 series switches, LightStream 1010 switches, or Cisco 7000 series routers, shown in the top-left and top-right corners, in a redundant configuration. If connectivity is lost to one of the backbone routers or switches, the network uses the redundant connection.
Spanning-Tree Protocol, available only on switches, ensures that only one of the two connections from each switch is active (the primary link), ensuring that there are no loops in the network paths. If the primary link fails, the secondary link becomes active.
The Catalyst 2820 switches in this example connect to the backbone switches or routers through the Catalyst 2820 single-port 100BaseT switch module in CollisionFree full-duplex mode or through the Catalyst 2820 ATM module. The distance between each Catalyst 2820 switch and the backbone switch or router can be increased to 2 kilometers by using a fiber-optic cable (full-duplex connection).
In Figure 1-8, two Catalyst 2820 switches, each with a Catalyst 2820 Fiber DAS module, connect to an FDDI network backbone. The Catalyst 2820 switch on the left also has a Catalyst 2820 4-port 100BaseT repeater module connecting two Catalyst 2820 switches and two servers via shared 100BaseT connections. (An 8-port 100BaseT repeater module is also available for the Catalyst 2820 switch.)
The three Catalyst 2820 switches on the right have Catalyst 2820 single-port 100BaseT switch modules and are daisy-chained to each other via a switched full-duplex 100BaseT connection. Two of the Catalyst 2820 switches on the right are also connected to single workstations, a server, and a 10BaseT hub. The 10BaseT hub supports more 10BaseT workstations that share the 10 Mbps of bandwidth between the workstations connected to this hub. The server is connected to the 100-Mbps port on the Catalyst 2820 switch and supports all the nodes connected to that switch.
A system of routers, switches, and hubs can be combined to create a high-performance network that extends beyond the main office LAN to connect to branch offices, remote sites, mobile users, and the Internet. Figure 1-9 is an example of an extended network.
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