Does switch drop untagged frames on tagged only port?


Userlevel 3
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)[/code]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,[/code]
[/code]

6 replies

Userlevel 3
A normal tagged port, will drop untagged frames if there no untagged vlans assigned.
Userlevel 3
Thanks!
but how will a switch forward an untagged frame to another switch if both are connected to each other ?
Userlevel 2
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
Userlevel 4
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...
Userlevel 6
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!
[/code]

Reply