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Spanning tree influenced HSRP Standby Priority?

a.kiprawih
Level 7
Level 7

Hi,

I have 2 x core switches with HA/redundancy (hsrp for vlans). The switches are linked via DOT1 trunk. 10 Vlans exists (vlan 1 to vlan 10). Core 2 hosts 3 active Vlans (with higher hsrp standby priority, lower in core2).

Example:

Core 1 ? Vlans with higher spanning tree (8192): 1,2,3,4,5,6,7,8,9,10

Core 1 ? Vlans with higher hsrp standby priority (150): 1,2,3,4,5,6,7

Core 1 ? Vlans with lower/default hsrp standby priority (100): 8,9,10

Core 2 ? Vlans with lower spanning tree (16384): 1,2,3,4,5,6,7,8,9,10

Core 2 ? Vlans with higher hsrp standby priority (150): 8,9,10

Core 2 ? Vlans with lower/default hsrp standby priority (150): 1,2,3,4,5,6,7

Some access switches are dual-homed to core1 and core2, others single-homed.

Both core1 and core2 host link to other sites - core1 to site A via a L3 device (sw1), core2 to site B via a L3 device (sw2).

Spanning tree priority for all Vlans are set higher (8192) in Core1, and lower in Core 2 (16384).

Questions:

1. Will the outbound traffic from vlan in core 1 with higher spanning tree priority and hsrp standby priority be affected if it wanted to go to site B which need to pass through the core2 switch?

2. Will the outbound traffic from vlan in core2 with lower spanning tree priority but higher hsrp standby priority be affected if it wanted to go to Site A which need to pass through the core1 switch?

3. Am I right to say that for the vlan design, Layer 2 should follow Layer 3 priority assignment, meaning if a Vlan is configured with higher spanning tree priority in core1, the hsrp standby priority must also set to higher. Is this a best practice approach?

The reason I asked is because :

1. I need to verify, specifically on the existing vlan design and priority assignment.

2. I encountered problems where a dual-homed switch belongs to Vlan with higher spanning tree and hsrp standby priority in core1 cannot reach site B (connected in core2). Same issues with to a vlan in core2 with lower spanning tree priority but higher standby priority that cannot reach site A via core1 switch. Even if the uplink to core1 is disconnected, hoping that route/path selection will automatically flow through core2, the traffic still unable to pass through.

Is the problem occurred due to difference in spanning tree and hsrp standby priority in core1 and core2 for the same vlan? The solution approach is to connect core1 to sw2, and core2 to sw1 directly (criss-cross) via routing port (L3).

Welcome any suggestions & input.

Thanks

AK

4 Replies 4

ananddiwakar
Level 1
Level 1