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we have switch catalyst 3850 and we need to enable the PXE boot on a port configured in trunk with configured three VLAN (4040, 4050 and 4060). To permit the PXE boot and deploy to work we set on the port channels the "switchport trunk native vlan 4040" this permit the PXE booting without the VLAN tag and also the deploy process proceed as expected.

What does not work as expected is the part after the deploy, the server is configured to send tagged traffic over the VLAN 4040, but seems that the switch refuse that traffic, if we remove the tag from the server the communications works.

Now the question, if the switch port are configured with the native VLAN 4040 will it refuse the traffic tagged on the VLAN 4040?

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The problem is not the traffic from the server to the switch, but the return traffic, from the switch to the server.

Since the VLAN is native, the switch will sent the traffic for this VLAN untagged, while the server expect it tagged.

So this cannot work as is.

You should probably use this VLAN only for PXE boot and configure your server Operating System to use a different, fully tagged VLAN.

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  • Thank for your answer, you clarify my doubt. if the deployment guys let work deploy with tag we are done like this, other else we will configure a VLAN dedicated for the deploy. – AtomiX84 Apr 14 at 10:13

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