STP vs LACP Redundancy

[ITGURU]

Can i just clarify something?

 

If i have a core switch which is built up of say 2 x switches in a ring stacking mode which are seen as 1 logical switch, can i use LACP for redundancy to another switch, as they are seen as 1 logical switch.

 

In this instance say an edge switch uses 2 x SFP ports back to the core, 1 connection into the core switch 1 and 1 connection into core switch 2.

 

If i use LACP this will form redundancy if one of the core switches fail?

 

Would STP just be required if both core switches were in standalone mode?

[FN-GM]

If they were 2 standalone switches you will need STP to make them act as active / passive. You would probably need to configure the core switch you want to be active by lowering the root bridge ID. By default if the root bridge value is the same it will use the lowest MAC address as the tie breaker. Sometimes this results in a undesirable switch becoming the root bridge and sending data down that undesirable switch. The core switch should be configured to be the root bridge anyway regardless to avoid this issue. If doing this you should also use something like rapid spanning tree.

 

If the switches are stacked and using LACP both LACP links will be active and be able to carry data. They can be used for redundancy. Although it’s worth noting spanning tree also applies to layer 2 LACP links to avoid loops.

Edited June 8, 2020 by FN-GM

[ITGURU]

If they were 2 standalone switches you will need STP to make them act as active / passive. You would probably need to configure the core switch you want to be active by lowering the root bridge ID. By default if the root bridge value is the same it will use the lowest MAC address as the tie breaker. Sometimes this results in a undesirable switch becoming the root bridge and sending data down that undesirable switch. The core switch should be configured to be the root bridge anyway regardless to avoid this issue. If doing this you should also use something like rapid spanning tree.

 

If the switches are stacked and using LACP both LACP links will be active and be able to carry data. They can be used for redundancy. Although it’s worth noting spanning tree also applies to layer 2 LACP links to avoid loops.

 

Thank you for the clarification!