Foundation Summary

Study Material For Cisco Ccna Ccnp And Ccie Students

Study Material For Cisco Students

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The "Foundation Summary" section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on your CCNA exam, a well-prepared CCNA candidate should know, at a minimum, all the details in each "Foundation Summary" section before going to take the exam.

Figure 10-11 shows the general idea of a VLAN, showing two different VLANs/broadcast domains.

Figure 10-11 Example Network with Two VLANs Using One Switch

Figure 10-11 Example Network with Two VLANs Using One Switch



With VLAN trunking, the switches tag each frame sent between switches so that the receiving switch knows what VLAN the frame belongs to. Figure 10-12 outlines the basic idea.

Figure 10-12 VLAN Trunking Between Two Switches


Figure 10-12 VLAN Trunking Between Two Switches



Figure 10-13 shows the benefit of using multiple VLANs, each with a separate spanning tree. Figure 10-13 ISL Per VLAN Spanning Tree (PVST)

Blocking - VLAN2 Blocking - VLAN1

Table 10-3 summarizes the key points about each type of switching. Table 10-3 Comparison of Multilayer Switching Options



Layer 2 switching*

The process of forwarding frames based on their MAC addresses.

External router, connected to L2 switch

Router forwards like always, based on destination IP address.

Layer 3 switch

Switch's forwarding logic forwards based on destination IP address for traffic destined for another VLAN.

Layer 4 switch

Can forward based on Layer 4 information, typically port numbers, but can also just do accounting based on L4 information.

Layer 5-7 switch

Forwards based on application layer information; typically considered a CDN feature.

Multilayer switch

A switch that concurrently performs switching based on multiple layers. For instance, most L3 switches also perform L2 switching inside a VLAN, and L3 switching for traffic between VLANs.

*L2 switching is the only option in the table that does not allow forwarding from one VLAN to another.

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