Switchport Access Mode VS Trunk Mode

Access Mode vs Trunk Mode

switchport access mode vs trunk mode

 

In this article, we will refer only to the Cisco platform switches like Catalyst series.

As a general case, freshers in networking domain (like CCNA aspirants etc.) tend to come across TRUNK and ACCESS terminologies in Switching.

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In most of Cisco switches, switchports are configured in “dynamic desirable” mode by default. This means if we connect devices, it will negotiate to form a trunk.

We can custom set switchports as either trunk or access mode since by letting default setting in place (the “dynamic desirable”), there will be less control on switch port behaviour.

Trunk ports are generally used in the switch to switch communication or switch to Router (Router on a stick). Trunks carry multiple Vlans across devices and maintain VLAN tags in Ethernet frames for receiving directly connected device differentiates between different Vlans.

Access ports are part of only one VLAN and normally used for terminating end devices likes PC, Laptop and printer.

Using the “Switchport mode access” command forces the port to be an access port while and any device plugged into this port will only be able to communicate with other devices that are in the same VLAN.

Using the “Switchport mode trunk” command forces the port to be trunk port.

Difference between Trunk port and Access port mode on Cisco Switches –

PARAMETER
TRUNK MODE
ACCESS MODE
Terminology
A trunk port can carry traffic in one or more VLANs on the same physical link. Trunked ports differentiate Vlans by either adding a tag to the packet (802.1Q) or encapsulation the packet (ISL).
Access ports are part of only one VLAN and normally used for terminating end devices likes PC, Laptop and printer.
Default Behavior (Cisco Switches)
By default, a trunk interface can carry traffic for all VLANs.
By default, an access port carries only one VLAN
Configuration
To designate a port to a trunk mode -
“Switchport mode trunk”
To designate a port to access mode -
“Switchport mode access”
Use case
Switch to Switch connectivity
Switch to Router (When using Router on a Stick or dot1q trunk)
Switch to Server (specific cases only especially in VM technology)
Switch to PC/laptop
Switch to Printer
Switch to Router
Note - This is typical standard procedure when such switch port serves end users such as PC, printer, or servers.
VLAN Tags
Port configured in Trunk mode will carry VLAN tags
Port configured in Access mode will not carry VLAN tags (stripped of VLAN tags)
Verification commands
Show Vlan brief
show interface x/x switchport
Show interface trunk
show interface x/x switchport

 

Download the difference table here.

 

 

 

 

 

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