Combining Hubs Switches and Routers

Available in Ethernet and Fast Ethernet, hubs are best used in small networks where there are few nodes on the segment. Hubs do not control the broadcasts nor do they filter collision domains on the network. If higher bandwidth is required, use 100 Mbps hubs. When the number of nodes on the network grows, move to switches.

With the cost of switch ports comparable to hubs, use switches as the basic network connectivity devices on the network. Switches reduce collisions and resolve media contention on the network by providing a collision domain per port. Replace hubs with switches if the utilization is over 40 percent on Ethernet networks or above 70 percent on Token Ring and FDDI networks. Switches cannot resolve broadcast characteristics of protocols; use routing to resolve protocol-related problems. As you can see in the sample in Figure 4-21, the repeaters are pushed to the outer layer of the design, connecting to switches. Switches control the collision domains. Fast Layer 3 switches are used for routing between LAN segments, and the router provides access to the WAN.

Figure 4-21 Combining Routers, Switches, and Hubs

Figure 4-21 Combining Routers, Switches, and Hubs

Network Operating System Diagram

Use routers for segmenting the network into separate broadcast domains, security filtering, and access to the WAN. If broadcast traffic on the network is over 20 percent, use routing.

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