Re: Which one is Open Standard and which one is Cisco based?
Paresh is correct.
Spanning Tree can operate in a single instance across the entire bridged network, independantly of VLANs (Cisco calls this Common Spanning-Tree (CST)), or can be run within each VLAN (Cisco?s Per-VLAN Spanning-Tree (PVST)), or selected groups of VLANs (Multiple Spanning Tree Protocol (MSTP) (IEEE 802.1s))
- CST reduces the CPU load on the switches, as they only need maintain once Spanning-Tree instance. It assumes a common, consistent layer-2 topology for all VLANs. The original 802.1Q standard uses CST.
- PVST requires more switch resources, however allows an elementary load-balancing through forwarding some VLANs on one trunk link, and others on other trunks (this is not an automatic process and requires manual configuration of port priorities for the selected VLANs).
- MSTP is the natural combination of CST and PVST - it allows a STP instance per group of VLANs. One significant difference over PVST is that MSTP sends only one BPDU for all STP groups.
-- MSTP has a couple of gotchas around assigning VLANs to MSTP instances - see Understanding Multiple Spanning Tree Protocol (802.1s) Document ID: 24248 for the pitfalls
- Cisco?s PVST (ISL) and PVST+ (802.1Q) implementations are proprietary, MSTP is standard (802.1s, now in 802.1Q-2003)
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
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