Does switch drop untagged frames on tagged only port?

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Hi everybody.

I have one question. It very important for me.

Let us suppose that I have tagged only port (I mean port where all vlans are tagged). What would switch do with received untagged frames?

sh ports 1 information detail 
Port:   1:
        VLAN cfg:
                 Name: Default, 802.1Q Tag = 1, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID:    1
                 Name: v4, 802.1Q Tag = 4, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID:    4
                 Name: v5, 802.1Q Tag = 5, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID:    5
                 Name: v6, 802.1Q Tag = 6, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID:    6
...
        Protocol:
        Trunking:       Load sharing is not enabled.
        Multi-switch LAG:               MLAG port (MLAG Id:  1)
And another case. I have tagged only port with VMAN vlan which untagged on this port. What would switch do with received untagged frames in this case?

sh ports 1 information detail 
Port:   1:
        VLAN cfg:
                 Name: Default, 802.1Q Tag = 1, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID:    1
                 Name: v2001, 802.1Q Tag = 2001, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID: 2001
                 Name: v2005, 802.1Q Tag = 2005, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID: 2005
                 Name: v2012, 802.1Q Tag = 2012, MAC-limit = No-limit, Virtual router:   VR-Default
                       Port-specific VLAN ID: 2012
        Protocol:
                 Name: v502         Protocol: ANY      Match all protocols.


sh vman v502
VMAN Interface with name v502 created by user
    Admin State:         Enabled     Tagging:   802.1Q Tag 502
    Description:         s2-VMAN
    Virtual router:      VR-Default
    IPv4 Forwarding:     Disabled
    IPv4 MC Forwarding:  Disabled
    IPv6 Forwarding:     Disabled
    IPv6 MC Forwarding:  Disabled
    IPv6:                None
    STPD:                None
    Protocol:            Match all unfiltered protocols
    Loopback:            Disabled
    NetLogin:            Disabled
    OpenFlow:            Disabled
    TRILL:               Disabled
    QosProfile:          None configured
    Egress Rate Limit Designated Port: None configured
    Flood Rate Limit QosProfile:       None configured
    Ports:   23.          (Number of active ports=10)
       Tag:      *25g
       CEP:   *1(PGS_C_16_1) : CVID 1100-1499,
                           CVID 2500-3999,

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eyeV

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Posted 4 years ago

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simon bingham

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A normal tagged port, will drop untagged frames if there no untagged vlans assigned.


(Edited)
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eyeV

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Thanks!
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Rahul Bhardwaj

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but how will a switch forward an untagged frame to another switch if both are connected to each other ?
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Chacko

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Well, you need to configure a vlan which has the same tag-id on both devices.
Then you can add both ports untagged to the vlan.

you can also configure a port to one untagged vlan and multiple tagged ones
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Tripathy, Priya Ranjan, ESE

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For more information on these tagged and untagged frames for tagged and untagged ports, you can have a look at the below articles for more understanding as well:

https://gtacknowledge.extremenetworks.com/articles/How_To/Understanding-EXOS-VLANS-and-tagged-and-un...

 
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Prashanth KG, Employee

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Hi,

Here are the answers to your questions:

1. Any untagged frames received on port 1 if all the VLANs are tagged will be dropped.

There has to be atleast one untagged VLAN on the port for this traffic to be forwarded.

2. As per your configuration of VMAN, port 1 is configured to carry the Customer VIDs.
CEP:   *1(PGS_C_16_1) : CVID 1100-1499,
                           CVID 2500-3999,

Which means, the traffic should come in with the tag values of 1100-1499 and 2500-3999. Again any untagged frames received on this port would be discarded.

If you could specify the requirement, we could help with the configuration tweak.

Hope this helps!