On a stacked 3750, I configured a trunk link (802.1Q) with a native VLAN 3:
switch(config-if)# switchport trunk encapsulation dot1q
switch(config-if)# switchport trunk native vlan 3
switch(config-if)# switchport mode trunk
Now I would expect to see plain (untagged) 802.1D BPDU's (not PVST+) to be sent to vlan 3 on this interface.
However, the PVST+ BPDU tagged for vlan 1 contains the same spanning tree payload
as the (untagged) 802.1D BPDU itself, indicating that they are intended for vlan 1.
Also shown by the root identifier 32769, which is 32768 + 1 (MAC address
(see native_untagged.cap packets 17,18)
When tagging is configured for all vlans including the native VLAN:
switch(config)# vlan dot1q tag native
the same 802.1D BPDU is now tagged for vlan 3.
To me it seems that it is tagged for the correct VLAN (3), but it
contains spanning-tree payload for the wrong VLAN (1).
(see native_tagged.cap packets 12,13)
Any comment on this ?
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