CCNA Certification/WAN< CCNA Certification
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WAN = Wide Area Network
WANs function at the physical and datalink layer of the OSI model. What differentiates a WAN from a LAN is the physical distance that a WAN can traverse while LANs are limited to buildings, WANs cover extensive geographical areas.
WAN interconnects physically distance LAN
WAN usually operate at the lower two layers of the OSI model, which is physical and datalink. Packet switching, circuit switching and leased lines are the valid WAN connectivity methods.
In a WAN the layer two address differs from the layer two address of the LAN. Since in a WAN the data is not traveling through the Ethernet, the valid encapsulations are DLCI for frame relay and HDLC (high level data link connection identifier).