Hi every body!
My book says pvst+ is commonly known as pvst, implying they are same but are known by two didderent acronymns.
However, my other book says PVST supports isl only therfore PVst speaking switch can not communicate with CST speaking switch.
PVST + supports both isl and dot1q.
So pvst+ acts as a translator between pvst based network and CSt based network.
So which concept or book is correct?
Thanks a lot!
PVST+ is an enhancement to run PVST over 802.1Q trunks and interact (or rather integrate) with third party bridges. Think of PVST+ as PVST v1.5. As soon as your bridge supports 802.1Q, it is a PVST+ bridge. So basically, all our switches are PVST+ and there is no real reason to make a difference between PVST+ and PVST. In my mind PVST = PVST+ and I rather use the term PVST as a counterpart to MST (rather than PVST+).
PVST+ has been introduced in Cisco CatOS 4.x current CatOS versions are 8.x 10 years ago or more according to first edition of CCNP switching exam (published in 2000 or 2001)
PVST+ introduced the proprietary BPDUs that can be tunneled via an 802.1D legacy CST switch over 802.1Q trunks.
PVST supported only ISL trunk links and couldn't interoperate with 802.1D CST switches.
Second book is right and PVST is not used anymore. I think I never used it.
Now that the focus is in comparing PVST+ and RPVST and MST some blurring between PVST+ and PVST is occurring in more modern books.
Hope to help