Our network has had no real need to use untagged traffic until recently. We have a new piece of equipment coming to our data center and it requires the use of untagged traffic through a trunked port-channel.
This is my understanding of how tagged and untagged traffic is handled by a switch.
When an untagged frame enters into an access port, if a VLAN is defined on the port (switchport access vlan 100), it will insert that tag into the header. If there is no VLAN defined, it inserts the native VLAN (VLAN 1) into the header for processing. If a tagged frame enters an access port, it will be dropped if it doesn't match the VLAN configured on the access port.
When an untagged frame enters a trunk port, it gets tagged by the native VLAN of that trunk. If any tagged frames enter a trunk port, only the VLANs configured on the trunk will be allowed, the rest will be dropped.
Basically, VLAN tags are applied at ingress of a port for untagged traffic, and VLAN tags are removed at egress of a port for untagged traffic.
I attempted to test this by taking a switch and configuring the ports 1 and 2. 1 is an access port on VLAN 100 and 2 is a trunk port configured with native VLAN 100.
interface GigabitEthernet1/0/1
switchport access vlan 100
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/2
switchport trunk native vlan 100
switchport mode trunk
!
I then connected a laptop to each port configured with IP addresses 10.1.1.2/24 and 10.1.1.3/24. When I attempt to ping from one device to the other, the pings fail.
What am I doing wrong? Am I misunderstanding how untagged traffic works? Am I missing something from my configuration?
Any assistance would be greatly appreciated.
