Hi Seunghak,
Please find the difference below;
1-Access-Ports:
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Access ports are what you would typically plug a server, PC/laptop, printer, etc into. An access port is configured to be within a particular VLAN. Ethernet frames that exit an access port (i.e. towards the device plugged into the port) will have any VLAN headers/tags stripped. Ethernet frames that enter an access port will have a VLAN tag added to identify which VLAN the ethernet frame belongs to.
2- Trunk Ports:
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Trunk ports are what you would typically plug a router into for inter-VLAN routing, or another switch in order to "share" VLANs between switches. Unlike access ports, ethernet frames that exit a trunk port will maintain any VLAN headers/tags that are present so that the receiving device is able to appropriately handle the frame.
Using the "switchport mode access" command you are, as mentioned by others, forcing the port to be an access port, no exceptions. A 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 you force the port to be a trunk.
By forcing the port into a particular configuration you will have predictable outcomes when you plug devices into those ports. Security wise its a good idea.
3- QinQ tunneling :
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This is the method basically used by service providers to preserve Vlan-Ids and to segregate
traffic of different customers.It enables service providers to use a single VLAN to support
different customers who have a single or multiple VLANs need to connect across providers
network.
More info on QinQ refer the following links:
http://ccienet.wordpress.com/2011/06/11/qinq-tunneling/
http://blog.ipexpert.com/2011/12/06/q-in-q-tunneling-for-the-ccie-rs-written-and-lab-exam/
HTH
Regards
Inayath
*Plz rate the usefull posts.
