Setting up Cisco Spanning Tree

We have a Cisco network, with a core router/switch (Cisco 6500) and then access switches (Cisco 2950s).  Currently we only have one connection from the core to the access layer.  (See drawing, Trunk 1 is in place today).

We'd like to add a backup connection (Trunk 2), that connects from the core to the last switch in the stack.  

Spanning-tree is currently enabled, but only the defaults.  I imagine simply plugging in the second trunk would work, but we want to make sure we're optimizing it.

I assume we want rtr1 (which is a layer2/3 device) should be the root bridge for all VLANs?  What would be the commands to force that?

Second, how do we force the traffic up the crossovers and through trunk 1?  Trunk2 shoudl be a backup, so we want to force it to blocking mode.  Do we just adjust the port cost on sw3 trunk 2 to something very high?

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If you are trying to optimize it, think about the fact that SW3 is directly connected to RTR1, so SW3 should be using that link instead of the old one to reach RTR1 because is the least cost path.
shanepresleyAuthor Commented:
Thanks, excellent advice.
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