3com 5500-ei pwr Instruccion De Instalación

 

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Figure 1-1 A VLAN implementation 

 

 

Compared with the traditional Ethernet, VLAN enjoys the following advantages. 

z 

Broadcasts are confined to VLANs. This decreases bandwidth consumption and improves network 

performance. 

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Network security is improved. Because each VLAN forms a broadcast domain, hosts in different 

VLANs cannot communicate with each other directly unless routers or Layer 3 switches are used.  

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A more flexible way to establish virtual workgroups. VLAN can be used to create a virtual 

workgroup spanning physical network segments. When the physical position of a host changes 

within the range of the virtual workgroup, the host can access the network without changing its 

network configuration. 

To enable a network device to identify frames of different VLANs, a VLAN tag field is inserted into the 

data link layer encapsulation.  

In 1999, IEEE issues the IEEE 802.1Q protocol to standardize VLAN implementation, defining the 

structure of VLAN-tagged packets.  

In traditional Ethernet data frames, the type field of the upper layer protocol is encapsulated after the 

destination MAC address and source MAC address, as shown in 

 

Figure 1-2 Encapsulation format of traditional Ethernet frames 

 

 

 DA refers to the destination MAC address, SA refers to the source MAC address, and Type 

refers to the upper layer protocol type of the packet. IEEE 802.1Q protocol defines that a 4-byte VLAN