Category: Switching

02

Jan2014

Why switch trunk/ tagged ports are used?

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Prior to 802.1q, switch vendors used proprietary methods to manage the transfer of VLAN tagged ethernet frames between switches.  These methods added the vlan to the frame  creating a proprietary frame.  Otherwise the other switch would put the frame in the vlan it's port was configured for. Each switch has the ... Read More
January 2, 2014Praveen Bahethi

28

Dec2013

Why do we use VLANs?

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Virtual Local Area Networks (VLAN) came about from the need to isolate broadcast domains with in a switch without using routers.  Router do not forward broadcasts, but back in the 90's they were not very fast compared to switches.  Router Layer 3 functions were done in processor and switch Layer ... Read More
December 28, 2013Praveen Bahethi

28

Dec2013

Why use link aggregation?

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Link aggregation protocols overcome spanning tree protocol's (STP) inherent design to block loops between switches by bundling of ports to appear as one logical connection to STP. With one logical connection, STP will not block the link but forward traffic.  Further the bundling can increase overall bandwidth between the switches. So ... Read More
December 28, 2013Praveen Bahethi

26

Dec2013

How is traffic forwarded at Layer 2 of the OSI model?

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Switches register the source MAC address seen on their ports to generate a MAC address table also known as Content Addressable Memory (CAM) table.   A MAC address table has the source MAC address the port that learned it a timer to aging out the VLAN the source MAC address belongs to When a switch ... Read More
December 26, 2013Praveen Bahethi