How prevent Spanning-Tree in this topology

[xyCruiseryx]

Hi all,

follow topology in attachment. The Vlan 1 is build with unmanaged switches. (this means no spanning-tree is possible). If in V1 a loop is produce, the managed switch and the router get an high utilization. This means the other network vlan 20 cant work too about the router in direction WAN too.

Why the managed Switch dont detect the loop below? (Spanning Tree is ena) What can i do to protect the other network (V20)on managed switch to work over the router.


Info: #

the managed Switch is a cisco-2950
the router is an cisco router

 

[BuckWeet]

If the managed switch supports broadcast/unicast flooding protection that is about the only thing you can do.. The loop causes inconsistent MAC tables, so the switch floods it out all ports. Then the high traffic rates take over and kill the CPU's of all devices.


BuckWeet

 

[vipergg]

All switches have to runn spanning tree in or for the network to protect itself against loops . The switches will then put one port in blocking mode esentially preventing the looping of data on your net. Seeing you only have a single switch that runs it all others below it are looped which is what is causing your problem . You either have to get managed switches that run spanning tree or take out a single connection between the switches at the bottom which takes out your built in loop.

 

[jneiberger]

I agree with the others. If you can't run STP, either replace those switches with some that do run it or manually remove one of the links.