Table of Contents
What does a network switch do?
Ethernet LAN switches use a very cool system called transparent bridging to create their address lookup tables. Transparent bridging is a technology that allows a switch to learn everything it needs to know about the location of nodes.
How does a switch work in a circuit?
Transparent bridging has five parts
Learning
Flooding
Forwarding
Filtering
Aging
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Learning
Suppose, A computer (node A) on the first segment (segment A) sends data to a computer (Node B) on another segment (segment C).
The switch gets the first packet of the data from Node A. It reads the MAC address and saves it to the lookup table for segment A. The switch now knows where to find Node A anytime a packet is addressed to it. This process is called Learning.
Flooding
Since the switch does now know where Node B is, it sends the packet to all the segments except the one that it arrived on (Segment A). When a switch sends a packet out to all segments to find a specific node, it is called Flooding.
Forwarding
Node B gets the packet and sends a packet back to Node A in acknowledgment.
The packet from Node B arrives at the switch. Now the switch can add the MAC address of Node B to the lookup table for segment C. Since the switch already knows the address of Node A, it sends the packet directly to it. Because Node A is on a different segment than Node B, the switch must connect the two segments to send the packet. This is known as Forwarding.
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Filtering
The next packet from Node A to Node B arrives at the switch. The switch now has the address of Node B too, so it forwards the packet directly to Node B.
Node C sends information to the switch for Node A. The switch looks at the MAC address for Node C and adds it to the lookup table for segment A. The switch already has the address for Node A and determines that both nodes are on the same segment, so it does not need to connect segment A to another segment for the data to travel from Node C to Node A. therefore, the switch will ignore packets traveling between nodes on the same segment. This is Filtering.
Aging
Learning and flooding continue as the switch add nodes to the lookup tables. Most switches have plenty of memory in a switch for maintaining the lookup tables; but to optimize the use of this memory, they still remove older information so that the switch doesn’t waste time searching through stale addresses. To do this, switches use a technique called Aging. Basically, when an entry is added to the lookup table for a node, it is given a configurable timer that erases the entry after a certain amount of time with no activity from that node. This frees up value-able memory resources for other entries. Transparent bridging is a great and essentially maintenance-free way to add and manage all the information a switch needs to do its job.
This is what network switch does in computer networking. And I hope you all understand that how to use a network switch.
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