VLAN question from Boson

BennyTheManBennyTheMan Member Posts: 76 ■■■□□□□□□□
I am confused about why an access port is not using 802.1q and supposedly will drop tagged frames.  Anyone able to explain this?  Please check out the screenshot.
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  • PCTechLincPCTechLinc Senior Member King City, CAMember Posts: 643 ■■■■■■□□□□
    A switch strips the tag off the frame before it sends out the port.  That is why an untagged frame is on the default VLAN.
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  • BennyTheManBennyTheMan Member Posts: 76 ■■■□□□□□□□
    Thanks for the info.  I'm honestly still confused, but I will continue to think it over.  
  • LunchbocksLunchbocks Senior Member FloridaMember Posts: 319 ■■■■□□□□□□
    edited January 5
    It drops all dot1q tagged traffic because the port is not a trunk. The first command sets the interface trunking type as dot1q, but only if trunking is configured. However, trunking is not configured. The "switchport mode access" command sets that interface as an access port, not a trunk port. An access port is a single vlan port, and is set to vlan 10 by the second command - "switchport access vlan 10".

    Hope this helps.

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  • BennyTheManBennyTheMan Member Posts: 76 ■■■□□□□□□□
    I thought if an access port is sending or receiving traffic, that traffic should be tagged for that specific vlan (vlan 10) in this case. I understand that it is an access port.  Thanks for helping.
  • LunchbocksLunchbocks Senior Member FloridaMember Posts: 319 ■■■■□□□□□□
    edited January 5
    No, tags are only on trunk traffic and not needed for access ports. Access ports are single VLAN ports and the switch knows which VLANs are associated with each port.

    A trunk port can pass multiple VLANs, and when passing traffic for multiple VLANs it needs a way to keep track of what VLAN each frame belongs to. So the trunk port adds the tag to each frame before putting it on the link. When the traffic reaches the next switch, the tag is removed and the traffic is forwarded to the correct interface port.

    Hope this helps.


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  • BennyTheManBennyTheMan Member Posts: 76 ■■■□□□□□□□
    edited January 5
    This is clear.  Is this saying that the switch will remove the vlan tag once the traffic crosses the trunk before going down the access port to the host?  I think I'm finally clear.  Really appreciate it!!
    Ben 
  • LunchbocksLunchbocks Senior Member FloridaMember Posts: 319 ■■■■□□□□□□
    It might actually be removed as it is going out the access port, but you have the concept correct now.

    Glad I could help.
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  • BennyTheManBennyTheMan Member Posts: 76 ■■■□□□□□□□
    Awesome.  Feels good to understand.
    Thank you so much.  On the grind to pass icnd2 before feb
  • LunchbocksLunchbocks Senior Member FloridaMember Posts: 319 ■■■■□□□□□□
    My pleasure. Good luck on ICND2.
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