Switching

Layer 2 and Layer 3 switches are used in both the Toronto and Seattle offices, as described in the following sections. (The security features implemented on the switches are described in the "Security" section, later in the chapter.)

Head-Office Switching

Within the Toronto office, Layer 2 switches are used in the Building access layer to provide connectivity for the users' laptops and IP phones. These access switches have inline power for the IP phones, and they redundantly connect to the collapsed backbone Layer 3 switches. The Spanning Tree Protocol (STP) is therefore not required, because no Layer 2 loop exists between the switches. As is normally recommended, though, STP should not be turned off, just in case a loop is configured in the future. To shorten the time it takes for the ports to come up, PortFast should be configured on each switch port that is connected to a laptop/IP phone combination.

IP phones with a built-in switch will be used; one port connects to the access switch and another connects to the laptop, as illustrated in Figure 12-6. The IP phone and laptop send traffic on two separate virtual LANs (VLANs); the connection to the access switch is an Institute of Electrical and Electronics Engineers (IEEE) 802.1q trunk, with the laptop on the native VLAN.

Figure 12-6. IP Phone with a Built-In Switch Connects to the Access Switch and User's Laptop

Note

In Figure 12-6, the connection between the laptop and the IP phone is not an IEEE 802.1q trunk. Data on this connection is all in a single VLAN; that VLAN is the native VLAN on the IEEE 802.1q trunk between the laptop and the access switch.

The Server module has Layer 2 access switches connected directly to the collapsed core.

The Toronto office also has Layer 3 switches, as shown earlier in Figure 12-2; the routing functionality required of these devices is described further in the "IP Addressing and Routing Protocol" section, later in the chapter. Because these switches are connected redundantly, the Gateway Load Balancing Protocol (GLBP) (as described in Chapter 10, "Other Enabling Technologies") should be used to allow both load sharing and redundancy.

Branch-Office Switching

The Seattle office also has Layer 2 switches, but because IP telephony is not used in this office, no special requirements exist for the switches. STP is again not required, because no Layer 2 loop exists between the switches. Just as in Toronto, STP should not be turned off, and PortFast should be configured on each switch port that is connected to a laptop.

Remote User Switching

The remote users do not require switches. However, users might have a router with a built-in switch (for example, a wireless broadband router with a built-in four-port switch can be used in an employee's home office).