While doing a review for one of the customer sites I've noticed a config, where the setup of the switches was: Switch 1 - Access VLAN 10 portfast <-> Switch 2 Trunk - Native VLAN 10;

Is there any specific reason for such config, or it's configured in incorrect way?


  • 1
    Without knowing more history, I can't say. But it is an erroneous configuration. (CDP should've err-disabled the link) – Ricky Jul 14 '16 at 23:15
  • That's not a very good way to do it. I'm sure whoever set that up thought there was a good reason to do it that way. Really, an access port should be set up to disable if it sees BPDUs come into it from another switch. – Ron Maupin Jul 14 '16 at 23:16
  • There's 0 incoming BPDUs on that port. Do you think that on the other side (Switch 2), there's a BPDU filter applied? – reybanger Jul 14 '16 at 23:49
  • No BPDUs means STP can't properly work, and that is a problem. – Ron Maupin Jul 15 '16 at 0:43

Generally that is a bad configuration. Perhaps someone just tried different things until something worked.

The other option was that they wanted to use the switch with the VLAN 10 access port as some kind of L2 fabric interconnect, but probably not.

You can do this if you are connecting between 2 separate VTP or administrative domains and it makes sense to do that, ie separate VLAN table on each switch.

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