STP and stacked switch

[Arjun Dabol]

Hi Experts

can someone please explain if there will be a need of STP when we have stacked switches. I understand that in LAN environment we will run STP but then we have firewall in between, so is it correct our stacked switched will be loop free. and will be considered a seprate topology altogether.

             Router

                |

SW1---stacked----SW2

                |

                |

      FIREWALL

               |

            LAN

Thanks

[Joseph W. Doherty]

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Posting

If you're referring to a stack of switches, like might be done with some 2960 models or the 3750, 3650 or 3850 models, the stack is logically one unit, and doesn't need STP to deal with its redundant stack links.

However, if such switch stacks, STP is always advisable to preclude someone accidentally L2 looping your switch.

[Arjun Dabol]

Thanks a lot. My design is attached . there is L2 switches (VLANs/LAN Network)  but below firewall . Do i need to consider STP. its a typical enterprise design.

My second Q is :

In this attached design : I am not able to understand why we need trunk between switch and router . AND why access between FW and switch. 

What kind of VLANs would exist there for which we need to create trunk ?

[paul driver · Accepted solution]

Hello

I guess the router is performing the inter-vlan routing and the interface linking the switch stack has subinterfaces relating to each vlan in your lan,

In that case you need the trunk to allowed multiple vlan information and tagged traffic across the interconnect.

res

Paul

res

Paul