Dell PowerSwitch S4048-ON, (rapid-)PVST, port-channels, and VLAN 1

AT ${WORK} we have a couple of stacked Dell PowerSwitch S4048-ON running PVST STP connected to a Cisco switch running rapid-PVST STP. TLDR; port-channels on the Dells needs portmode hybrid in addition to switchport to enable VLAN 1, and it helps to ignore “invalid” PVST-BPDUs by adding no spanning-tree pvst err-disable cause invalid-pvst-bpdu to the port-channels.

PVST on the Dells should be configured as:

protocol spanning-tree pvst
 bridge-priority 32768
 no disable
 extend system-id

Now, let’s get VLAN 1 up & running between the Dells and the Cisco.

! 1. Remove all VLANs served by said port-channel.
interface vlan 2
no tagged interface port-channel 3
interface vlan 3
no tagged interface port-channel 3

! 2. Make the port-channel L3, add portmode hybrid,
!    and return to L2.
interface port-channel 3
no switchport
portmode hybrid
switchport
no spanning-tree pvst err-disable cause invalid-pvst-bpdu

! 3. Add the previously removed VLANs to said
!    port-channel.
interface vlan 2
tagged interface port-channel 3
interface vlan 3
tagged interface port-channel 3

end
wr
exit

By now, VLAN 1 should be forwarded as an untagged VLAN between the switches.