Posted on September 22, 2020 11:23 am
 |  Asked by Alex Baker
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I’m not sure how this happened but I configured some trunk interfaces on a switch I manage last week, assigning them a range of 5 VLANs. Somehow they are now allowing traffic from every VLAN on the switch and show up under every VLAN.

Here’s the config I have running on one of the interfaces:

interface Ethernet4/10/1
speed forced 25gfull
switchport trunk native vlan 1700
switchport trunk allowed vlan 1701-1704
switchport mode trunk

When I do a “show vlan” command, this interface is listed on every single VLAN.

I’m assuming I did something wrong, not sure what.

Answered on September 22, 2020 11:28 am

Hi Alex,

Thanks for reaching out.

I have checked it on few platform models with different EOS versions and it worked fine in the lab and is allowing only particular vlans mentioned by the command "switchport trunk allowed vlan."

Could you please provide the output of "show tech-support | no" from the device to check and test this in the lab for that particular model and version?



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