I'm trying to find some good web reading that gives a brief intro/tutorial to VLANs and various techniques used to tag the frames. I thought that the frames were tagged by which physical port switch port they entered.
We are looking at upgrading our infrastructure to support VoIP, and am trying to grasp all the new tagging info for VLAN. Currently have older cisco 2501 routers and HP switches. Moving to 2801 routers and ?? switches.
Are there different ways of tagging frames today basaed upon different standards, that were not around a few years ago ?
Can switches from different vendors all play nice together ?
What happens to tagged frames vs un-tagged frames ? What if a frame doesn't have the extra 4-bytes for VLANs, what about a tagged frame going thru an old legacy switch that doesn't know about the extra bytes ?
How does a frame obtain the VLAN ID - where does it come from ? Only from physically connecting to a specific switch port ? I've read abotu DHCP handing out VLAN ID - How ?
And lastly - and most important - How does a VoIP phone, with it's internal 2-port switch create a VLAN ID for the phone's ethernet port, and a different one (or just untagged ?) for the connected PC ?
How does it all work when the phone is just physically moved, and plugged into a different wall jack - hence a different switch port ?
How does DHCP enter into this picture ?