cegner wrote:For me, it _does_ revert. But I don't get why I loose access at all. It's seems to be a bug.
Its not a bug, you lose access because something is configured wrong and it reverts after the specified period to the previous config as designed.
I am not sure why you do not understand that if the network and switch are responding correctly and then you change a U to a Q that other changes will have to take place on other equipment talking to the switch before it will function correctly again?
Changing a U or T to a Q on a port is big change in VLAN topology and will
require other changes to occur with the equipment on either end of the switch to function properly.
If the port was a U and now is a Q the behavior of how packets are handled changes vastly.
If it was a U the port expected to receive Untagged packets but now as Q if it receives a packet which could be Untagged or Tagged it will encapsulate it within an outer VLAN Tag.
If it was a U the port stripped all VLAN Tags off when packets leave the port but now as a Q it will only strip off the outer Tag leaving a second inner Tag intact if one exists or simply pass a now non tagged packet.
If it was a T the port would only accept Tagged packets with the proper VLAN ID but now as a Q it will accept ALL packets and encapsulate them inside a VLAN Tag, if it was already a Tagged VLAN packet it is now nested under the new outer VLAN packet ID.
If it was a T then packets leaving the port would be left intact with their VLAN Tag(s) but now as a Q it will strip the outer VLAN Tag leaving either a simple 802.1q VLAN Tag or an Untagged packet if it was not a nested VLAN or QinQ.
So when changing a T or U to a Q it REQUIRES configuration changes to occur to devices on either side of the switch to now deal which what is going to happen to the packets as the behavior has completely changed.