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New Member

How to configure STP on Cisco 3750 Switches.

Hi All

I have 10 cisco Switch 3750 in LAN. All these are in connected in Ring. All those are configured with multiple VLAN's and Routing is also enable. I want to enable STP on all these switches. In case if any links drop between two switches and auto backup from other side.

I would apperciate if anyone can help.

Thanx

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: How to configure STP on Cisco 3750 Switches.

STP is enable by defualt

you can chek it by using the command : show spanning-tree vlan 1

the defualt span mode is : PVST+ (peer vlan spanning-tree)

9 REPLIES
New Member

Re: How to configure STP on Cisco 3750 Switches.

STP is enable by defualt

you can chek it by using the command : show spanning-tree vlan 1

the defualt span mode is : PVST+ (peer vlan spanning-tree)

New Member

Re: How to configure STP on Cisco 3750 Switches.

Thanx for reply,

yeah this is right, By default this is enable on cisco Swiches 3750.

I want to make one switch as a Root Switch and others as client.

so does i need to configure only my Root Switch for STP or i will enable on all switches.

New Member

Re: How to configure STP on Cisco 3750 Switches.

By default STP will choose one switch as root bridge.

Any switch you want elected as root bridge for all vlan do the below configuration on it

sw 1 (config) #spanning-tree vlan (vlans id e.x:1,3-5) root primary

if you if this switch go down and you don’t want STP calculate and choose any switch

you can go to second switch and use :

sw 1 (config) #spanning-tree vlan (vlans id e.x:1,3-5) root secondary

New Member

Re: How to configure STP on Cisco 3750 Switches.

It mean i need just  configure only root Switch and did disable STP on other switches ?

New Member

Re: How to configure STP on Cisco 3750 Switches.

No ,

STP :

why using STP : to prevent L2 loop

How : by find one single path between two switches.

,,,,,,,,,,,,,,,,,,,,,

in STP domain must one switch come root bridge.

so you don’t need disable in other switches

My recommendation keep the STP as is . And read about STP protocol

New Member

Re: How to configure STP on Cisco 3750 Switches.

Please note that STP is limited to 7 successives links.

So in your case (10 swoiches in ring), I am afraid the topology could

not be computed in case of failure of one link.

New Member

Re: How to configure STP on Cisco 3750 Switches.

I Agree with that. It is known that STP start making issues once the ring goes beyond 6 or 7 switches.

If your Vlans are all local to one switch (ex. sw 1 has vlan 20,30. sw 2 has vlan 40,50). then i would recommend to change the connecting links to routed ports and just do proper routing between. the routing protocols will take care of loops/convergence in case of link failures.

New Member

Re: How to configure STP on Cisco 3750 Switches.

All the core(3750) switch are connected on trunk and Distribution(3500/2950) switch are also connected on trunk with core switch(3750), then on Distribution switch  (3500/2950) srw/Netgare are connected through VLAN

New Member

Re: How to configure STP on Cisco 3750 Switches.

drawing could be nice. didnt understand the topology.

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