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Network Port Trunking

In telecommunications, trunking is a method for a system to provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of this include telephone systems and the two-way radios commonly used by police agencies. More recently port trunking has been applied in computer networking as well.

A trunk is a single transmission channel between two points, each point being either the switching center or the node.

in our switching lab example we are using 3 switchs which are connected to each other , all those ports need to become as trunk port to pass all broadcast network\domain traffic between switch , because we wish to use same VLANs (Broadcast Network) between switch so to pass all VLANs traffic from a single port you need to made that port as Trunk port.

So in This example:
Switch 1 port F 0/11 is connected to Switch 3 port F 0/12 and port F 0/12 is connected to switch 2 port F 0/12.
Switch 2 port F 0/11 is connected to Switch 3 port F 0/11 and port F 0/12 is connected to switch 2 port F 0/12.
Switch 3 port F 0/11 is connected to Switch 2 port F 0/11 and port F 0/12 is connected to switch 1 port F 0/11.

to Enable a port as Trunk port you need to do the fallowing

when you enable trunk port all VLANs Pc´s start communicating which are in same VLAN .
it meaning VLAN 5 PC will communicate with VLAN 5 PCs
VLAN 6 PC will start communication with VLAN 6 , but VLAN 5 PC will not communicate with VLAN 6 Pc even the connected to same switch which have Trunk Port enable .