Switch Stacking Concept

Switch stacking is a method of binding multiple switches so that they can act as a single switch. This method is applicable on access layer switches. Now you wonder what are these access layer switches? 

Actually there are three types of switches in a LAN. These are Core, Distributed layer and Access layer switch.

Switch Type Description
Access layer switches Switches which are connected to the end user devices.
Distribution layer switch Switches which connects all access layer and core switches. They distribute network traffic from core to access layer switches. They are generally more powerful than access layer switches.
Core switches These are inner most switches in a LAN. All the LAN network traffic arrives at this switch through Edge router and then it transfers the traffic to distribution layer switches. 

Figure- Switches type in LAN

Imagine that you are network administrator and have to setup a LAN in a multistorey office building. There will be a large no of access layer switches and you have to configure almost similar configuration on switch each one by one. In real world, switches sits in a wiring closet. They are placed close to each other in wiring closet. One of the switches is responsible of all type of operations of the stack and is called the stack master. The stack master along with other switches in the stack are stack members. It show the whole switch stack as a one device to the network. Configuring all switches may be headache & time consuming. Hence, to deal with these situation a switch feature called switch stacking is used to combine switches placed in a wiring closet. This feature allows Network Engineer to make a stack of switches in a single wiring closet.

To make use of all benefits, switches have special hardware and interface available in them. A special type of network is used to connect the switches in a stack. Switches have a special dedicated port for stacking purpose and they are called stacking port. A stack of switches are connected to each other through stacking ports in a cyclic manner.



Figure – CISCO Catalyst 3750 Switch stack 

Benefits of using Switch Stacking : 

  1. All switch ports appears to be part of single switch.
  2. Single MAC-address Table to maintained by stack of switches.
  3. The stack have a single management IP address.
  4. All switches can be managed by single management IP.
  5. Various protocols like STP,OSPF run on single switch, not on all switches.
  6. Single VLAN management.
  7. The whole switch is managed as a 1 switch, including all the passwords, VLANs and interfaces. 
  8. Whenever we want to add a new switch to the stack, the master switch automatically configures it. 
  9. Cost and time efficient. 
     

Where we need to use Switch Stacking ? 
Let’s Consider small situation where a company have 32 ports switch. Now company wants 40 ports switch instead of 32 ports switch. The company can handle this situation in 2 ways: 
 

  1. Company can buy new 40 ports switch and reconfigure it from initial phase (It take more cost to buy and take extra time to configure it.). 
     
  2. Company can add another 8 ports switch to the existing 32 ports switch using the concept of switch stacking. 
     

Company may prefer to go for 2nd option as it is cost efficient and requires low man power and time.
 

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