I have kind of an odd situation here. The router and our uplink was configured with the native vlan being 839. Our aggergate fiber switch, and all those attached to it, was configured with the native vlan being 829. Ooooppps. It has been like that for almost 10 years, I don't know why it works, but it does. Oh, and I wasn't here 10 years ago. We are getting the correct subnet, DHCP services, and are getting full access to the outside world where we shouldn't. The uplink is a plain access port, no trunks. I find it all a bit confusing. I am not getting any mismatch errors, and cdp is running. I can't see how the router is configured as it is managed by a different group. Does anyone happen to know why this is working? All the ports are configured as vlan 829 on our switches, so traffic isn't being carried by vlan1. ???
The VLAN tagging is applicable only on a trunk interface. So, when traffic moves from one switch to another, at that time your VLAN tagging comes into picture. One the traffic enters the switch, the TAG will be removed and will be forwarded based on the MAC addresses. So, in your scenario, between all your access switches, traffic goes tagged and the traffic belonging to native vlan (829) goes untagged. When the traffic hits the core switch, it gets routed and the traffic then goes to VLAN 839. So, there is no issue with the Native VLAN.
Hope this answers your questions.