Cross-stack Etherchannel 20Gb and STP on 3750x

[Pierluigi Torriani]

    Hi,

i want to realize a 20gb ring stp with 6  3750x stacked by 2.

I want to install 2 3750x stacked configured in hsrp mode with other 2 3750 stacked. These 2 different stack are interconnected by a cross-stack etherchannel 20Gb  fiber. On the other side of the room i want to create a new stack with 2 3750x with cross-stack etherchannel 20gb connected with the previous 2 stacks. So, in total 3 different cross-stack etherchannel 20Gb stacks interconnected creating a ring stp of 20 Gb.

This configuration in your opinion can work correctly?

Thanks

Pierluigi

[acampbell]

Hi,

As it sounds like you will be installing a physical ring the best practice would be

to avoid the chances of STP loops

May be try to configure something like this :-

                                    2x10GB AS PORT CHANNEL

3750X-STACK1===================================3750X-STACK2

STP ROOT ODD VLANS                                        STP ROOT EVEN VLANS

HSRP ACT ODD VLANS                                        HSRP ACT EVEN VLANS

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      |                                                                                           |

      ===============3750X-STACK3====================

2x10GB AS PORT CHANNEL            2x10GB AS PORT CHANNEL

HTH

Alex

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[Pierluigi Torriani]

Thanks for your answer. You understand correctly, but i attach a jpg to axplain the final configurazion.

In your opinion this configuration can work correctly or not? There may be some problems?

Thanks

Pierluigi

[acampbell]

Pierluigi

I do not see any issue with your set up.

But as I showed above it is better to design & config with loop avoidance

STP root bridge selected for each vlan

Something like this :-

SWITCH-1 (PRIMARY FOR ODD VLANS)
!
spanning-tree mode rapid-pvst
spanning-tree vlan 1,3,5,7,9  priority 8192
spanning-tree vlan 2,4,6,8,10  priority 16384
!

SWITCH-2 (PRIMARY FOR EVEN VLANS)
!
spanning-tree mode rapid-pvst
spanning-tree vlan 2,4,6,8,10  priority 8192
spanning-tree vlan 1,3,5,7,9  priority 16384
!

SWITCH -3 Leve priority as default 32768

HTH

Alex

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[Pierluigi Torriani]

  Ok,

thanks for your support.

Pierluigi