Loop avoiding in Management LAN

[amitkverma24]

Hi all,

We have following scenario

1. Having Five up links From Core Switches (HP make)  to 5 different cisco switches through CAT cables.

2. From 5 Cisco switches ; IP phones, PCs, Thin clients , Terminal servers and LAN extenders are connected through cat cable.

3. From each Cisco Switches ----> one Un-manged  Switches are also connected through cat cable. 

How ever, We had configured Spinning tree port fast  in all edge ports.

I am very New to networking.Please suggest , How to avoid loop in this scenario.

[Mark Malone · Accepted solution]

Hi
STP will automatically prevent a loop by setting some of your links to blocking mode , you could also manually make the links block themselves if you don't want STP to automatically do it , by setting the cost under the links between switches to be high like spanning-tree cost 5000 , that would make a link go into blocking mode if there was one other available with lower cost , you should us bpduuard with your portfast config , the more control you have over STP when it fails the quicker the convergence will be , the unmanaged swtch may cause an issue if does not understand BPDU traffic , where is this located in the topology ? Unmanaged switch really not recommended if it doesn't understand BPDU , the network will still operate but not as well in terms of STP , so if there was a loop say in the unmanaged switches the STP running on the other switches won’t do anything regarding it , check do the unmanaged switches run BPDU at any level

[amitkverma24]

Thanks Mark.

Did not face loop so far.