Hello Naveen,
if we have a LAN infrastructure but with no redundant links between the switches, how the stp election proceeds. wether it happens or not.
The STP process always takes place, even if there are no redundant links in your topology. STP can not know about that beforehand - it will only find out after going the entire usual process of root bridge/root port/designated port elections.
What is the difrence between PVST and PVST+
We talk about PVST when we talk about sending and receiving STP BPDUs for separate VLANs over ISL trunk links. Conversely, we talk about PVST+ when per-VLAN STP BPDUs are being sent and received over 802.1q trunk links. This distinction is made for a couple of purposes:
- On ISL links, you do not need to care much about the non-PVST network region and cooperating with it because there is no need for that - ISL is Cisco proprietary and whatever is connected to an ISL link must be a Cisco device in order to understand - and Cisco supports the PVST out of the box.
- On 802.1q links, there is a series of things to take care about:
- Cooperating with possible non-PVST+ region connected to this link, i.e. blending with non-VLAN-aware STP run by ordinary switches
- Dealing with the possibility of native VLAN mismatch and the resulting misprocessing of BPDUs that have been originated in one VLAN and received/processed in another
You may be interested about reading about these kinds of inconsistencies here:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml
Best regards,
Peter
