TRUNKING: CONCEPT: PORT TYPES, WHAT, ENCAP TYPES?


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TOPICS

WHAT IS ACCESS AND TRUNK PORT?

WHAT IS TRUNKING?

ENCAPSULATION TYPES

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WHAT IS ACCESS AND TRUNK PORT?

Access Port: which allows traffic of only one VLAN

Trunk Port: which allows traffic of more than one VLAN

By default, in a new switch all ports are access port

Command to make Access port: switch port mode access

Command to make Trunk port: switch port mode trunk

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WHAT IS TRUNKING?

Trunk links provide VLAN identification for frames travelling between switches

Most common scenario, where you will see the Trunking Process

 

EXAMPLE:      SWITCH-A(F0/1)————(F0/0)SWITCH-B

Here, we have two switches A and B

we have n number of VLAN’s distributed accross both the switches

So, communication between VLAN’s is required on these two switches

 

To allow communication between two switches, TRUNK LINK BETWEEN SWITCHES SHOULD COME UP

CONDITIONS ARE:

–> Make F0/1 on SWITCH-A  and   F0/0 on SWITCH-B as Trunk ports

–> Native VLAN for both the Trunk Ports should be same

–> By default, all VLAN’s are allowed. To allow specific VLAN, use command: switchport mode trunk allowed vlan <vlan numbers>

–> Encapsulation should be the same on both the sides, either ISL or 802.1 Q, depending on scenario

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ENCAPSULATION TYPES

we have two options ISL or 802.1Q

ISL is Cisco Proprietary

802.1Q is open standard

ISL is having double tagging, added payload is 30 bytes. Double tagging is done at Header and Tailer

802.1Q is having single tagging. Single tagging is done inbetween the data

ISL donot allow untagged data

802.1Q allows untagged data

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