Key Features and Benefits

The Catalyst 3900 has the following features:

Twenty shielded Token Ring ports for 150−ohm shielded twisted pair (STP) or 100−ohm unshielded twisted pair (UTP) connectivity

FlexSlot accommodating two expansion modules or one double−wide module for future expansion

Nine−pin EIA/TIA−232 interface for local console or modem connectivity

Automatic 4−, 16−, and 32Mbps speed adaptation

TokenChannel switch interconnect

MAC address and protocol (DSAP/SNAP) filters

IEEE and IBM Spanning−Tree Protocol

The Catalyst 3920 provides the following features:

Twenty−four shielded Token Ring ports for 150−ohm STP or 100−ohm UTP connectivity

Nine−pin EIA/TIA−232 interface for local console or modem connectivity

Automatic 4−, 16− and 32Mbps speed adaptation

TokenChannel switch interconnect

MAC address and protocol (DSAP/SNAP) filters

Spanning−Tree Protocol

When you need to upgrade the Catalyst 3900 or 3920 IOS, you can do so by using the same serial port that is used for configuration. You can upgrade code by using Trivial File Transfer Protocol (TFTP) from a TFTP server or uploaded through the workstation using HyperTerminal. Table E.7 shows key features of the Catalyst 3900 series.

Table E.7: The key features of the Cisco Catalyst 3900 series.

Feature

3900

3920

Ports

20/24/28

24

Stack slot

1

1

Expansion slots

1 FlexSlot

None

Backplane

520Mbps

520Mbps

Processor

Intel 960SA

Intel 960SA

DRAM

Up to 8MB

Up to 8MB

Stackable

Yes

Yes

Distribution Layer Switches

The Distribution layer is the demarcation point between the Access and Core layers. This level terminates the traffic that originates in the Access layer connections and summarizes the traffic before passing it along to the Core layer. It can best be described as the layer that provides policy−based connectivity.

The main focus of the Distribution layer is to define the boundaries for the network and to provide packet manipulation of the network traffic. It provides isolation from topology changes, manages the size of the routing table, and aggregates network traffic.

In addition, interdomain traffic is redistributed at the Distribution layer, and static and dynamic route redistribution occurs at this point. This layer is also commonly used as the point at which remote sites connect to the network. Let’s take a look at the different switches typically found at this layer.

In this section we’ll be looking at the following switches:

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Cisco Systems RJ-45-to-AUX manual Distribution Layer Switches, Key Features and Benefits, Up to 8MB Stackable Yes, 364