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Regarding cascading 2960 switches

smothuku
Level 7
Level 7

Hi Experts ,

I would like to know the maximum number 2960 switches can be cascaded.

How many 2960 swutches we can connect in cascaded position.Is there any doc.

Thanks,

Satish

3 Replies 3

satish_zanjurne
Level 4
Level 4

Hi,

The conservative default values for the STP timers impose a maximum network diameter of seven. This maximum network diameter restricts how far away from each other bridges/switches in the network can be. In this case, two distinct bridges/switches cannot be more than seven hops away from each other

When a BPDU propagates from the root bridge toward the leaves of the tree, the age field increments each time the BPDU goes though a bridge/switch. Eventually, the bridge discards the BPDU when the age field goes beyond maximum age. If the root is too far away from some bridges/switch of the network, this issue can occur. This issue affects convergence of the spanning tree.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800951ac.shtml

So it's 7 !!!

HTH..

Hi Satish ,

Thanks for the info.Is there any doc which specifies switch model and max.limit of switches can be connected in cascade position.

Thanks,

Satish

Use the diameter keyword to specify the Layer 2 network diameter (that is, the maximum number of switch hops between any two end stations in the Layer 2 network). When you specify the network diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age time for a network of that diameter, which can significantly reduce the convergence time. You can use the hello keyword to override the automatically calculated hello time

this is the document.

http://cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_44_se/configuration/guide/swstp.html#wp1020804

Command is :

spanning-tree vlan vlan-id root primary [diameter net-diameter [hello-time seconds]]

(Optional) For diameter net-diameter, specify the maximum number of switches between any two end stations. The range is 2 to 7.

HTH..

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