VinceWhirlwind
Technical User
Can anybody help me get my head around this? I have never needed to use PVST before but now I'm having to consider it due to the horrible LAN design I'm facing.
I have a ring of 4 switches.
PVST+ enabled.
Switch 1 is at the top, 2 & 3 are each connected to 1, and 4 is at the bottom connected to 2 & 3.
Switch 1 is priority 4K and always wins Root bridge election.
Switch 1 is the router "core". All others are layer2 only.
All links are 10Gb = cost 2k
I have 2 user VLANs.
The Users are all on Switch4.
User VLAN1 mostly accesses a server that is on Switch 3
User VLAN2 mostly accesses a server that is on Switch 2
Each VLAN is carried between switches on a dedicated physical link.
ie, there are two links between Switch1 & Switch2, one is in VLAN1 and the other is in VLAN2.
So, from a traffic management point of view, I can avoid all traffic going through the "core" switch if I can have
- the link between Switch 4 & Switch 2 active for User VLAN2
- the link between Switch 4 & Switch 3 active for User VLAN1.
So, I put VLAN1 in PVST instance 1 and VLAN2 in PVST instance 2.
Then, I put Switch4 VLAN1 switchport connecting Switch2 a PVST cost = 20,000
I put Switch4 VLAN2 switchport connecting Switch3 a PVST cost = 20,000
So the higher cost interfaces become blocked, and I end up on Switch4 with the a Root port for VLAN1 that's facing one way, and the root port for VLAN2 facing the other way.
Is that how it works?
I have a ring of 4 switches.
PVST+ enabled.
Switch 1 is at the top, 2 & 3 are each connected to 1, and 4 is at the bottom connected to 2 & 3.
Switch 1 is priority 4K and always wins Root bridge election.
Switch 1 is the router "core". All others are layer2 only.
All links are 10Gb = cost 2k
I have 2 user VLANs.
The Users are all on Switch4.
User VLAN1 mostly accesses a server that is on Switch 3
User VLAN2 mostly accesses a server that is on Switch 2
Each VLAN is carried between switches on a dedicated physical link.
ie, there are two links between Switch1 & Switch2, one is in VLAN1 and the other is in VLAN2.
So, from a traffic management point of view, I can avoid all traffic going through the "core" switch if I can have
- the link between Switch 4 & Switch 2 active for User VLAN2
- the link between Switch 4 & Switch 3 active for User VLAN1.
So, I put VLAN1 in PVST instance 1 and VLAN2 in PVST instance 2.
Then, I put Switch4 VLAN1 switchport connecting Switch2 a PVST cost = 20,000
I put Switch4 VLAN2 switchport connecting Switch3 a PVST cost = 20,000
So the higher cost interfaces become blocked, and I end up on Switch4 with the a Root port for VLAN1 that's facing one way, and the root port for VLAN2 facing the other way.
Is that how it works?