A router is a layer device, which means it makes forwarding decisions based on logical network address (for example, IP address) information. Although a router is considered to be a layer 3 device, like a multilayer switch, it has the capability to consider higher-layer parameters, such as quality of service (QoS) settings, in making forwarding decisions.
Figure 9-15 Router Broadcast and Collision Domains
As shown in Figure 9-15, each port on a router is a separate collision domain and a separate broadcast domain. At this point in the discussion, routers are beginning to sound much like multilayer switches. So, why would network designers select a router rather than a multilayer switch in their design?
One reason a router is preferable to a multilayer switch in some cases is that routers are usually more feature rich and support a broader range of interface types. For example, if you need to connect a layer 3 device out to your Internet service provider (ISP) using a serial port, you will be more likely to find a serial port expansion module for your router than for your multilayer switch.
About The Author
Anthony Sequeira, CCIE No. 15626, is a Cisco Certified Systems Instructor (CCSI) and author regarding all levels and tracks of Cisco Certification. Anthony formally began his career in the information technology industry in 1994 with IBM in Tampa, Florida. He quickly formed his own computer consultancy, Computer Solutions, and then discovered his true passion-teaching and writing about Microsoft and Cisco technologies. Anthony joined Mastering Computers in 1996 and lectured to massive audiences around the world about the latest in computer technologies. Mastering Computers became the revolutionary online training company, KnowledgeNet, and Anthony trained there for many years. Anthony is currently pursuing his second CCIE in the area of Security and is a full-time instructor for the next-generation of KnowledgeNet, StormWind.com. Anthony is also a VMware Certified Professional.
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More Networking Topologies Articles:
• Hubs, Switches and Routers - What's the Difference?
• Routing Technologies, Bandwidth Management and Traffic Shaping
• A Guide to Broadband Internet Connections
• The Difference Between a Broadcast Domain and a Collision Domain
• What is FTTP, FTTH, FTTB, and FTTD?
• Cable: Cat5, Cat5e, Cat6, Cat6A ; What's the Difference?
• What Are Fiber Optic Isolators?
• The IEEE 802.3 Ethernet Standards
• Overview of IEEE 802.11 Wireless Lan Technology
• Beginners Guide to Fiber Optic Bit Error Ratio (BER) Measurement