Mocomtech CRS-300 operation manual Introduction, Ethernet Routers vs. Switches

Chapter 3. ETHERNET NETWORK CONFIGURATIONS

3.1Introduction

For operations requiring Ethernet-based terrestrial data handling, it is important to emphasize the need for Users to avoid Ethernet looping connection problems – with or without use of the CRS-300 1:10 Redundancy Switch.

The intent of this chapter is to outline the differing methods for Ethernet-based data handling with the various modems featured throughout this manual. Additionally, this chapter outlines use of the CDM-700 Satellite Modem in redundancy. The CDM-700 provides the added functionality of multiple data type handling simultaneously with Ethernet; i.e., Ethernet & HSSI, Ethernet & G.703, etc.

3.2Ethernet Routers vs. Switches

Routers and switches allow connection of one or more computers or networked devices to other computers or network devices. Each has two or more connectors, called ports, in which cables connect to other network devices.

An Ethernet switch examines the traffic that comes across it, and learns where particular MAC addresses are. An Ethernet switch maintains what is known as a CAM (Content Addressable Memory) table, listing the MAC addresses for each switch port. The Ethernet switch uses the CAM table to determine where to forward Ethernet frames. By default, Ethernet switches will update the CAM table automatically; for example, if an Ethernet switch sees traffic from ‘Machine A’ coming in on ‘Port 2’, it now knows that ‘Machine A’ is connected to that port, and that traffic destined for ‘Machine A’ needs to only be sent to that port and not any of the others.

An Ethernet router determines where to forward IP traffic based upon the destination IP address and the Route table entries in the router. An Ethernet router can be programmed to understand and route the data it is directed to handle; for example, broadband routers include the ability to "hide" computers behind a type of firewall, which involves slightly modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic: larger routers include the equivalent of a full-blown programming language to describe how they should operate, as well as the ability to communicate with other routers to describe or determine the best way to direct network traffic from ‘Point A’ to ‘Point B’.

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