placement root bridge

[hmc2500]

Please see attached image. the site is wired a little weird. Which switch is best to make the root switch in the branch office? switch1? L3 switch? 

[Georg Pauwen]

Hello,

what type(s) is/are the switches ? Usually the most powerful swiitch would be in the center of the network, and that would be the root switch...so in your image, that could be Swiych 1, but if the L3 switch is a higher, more advanced model, that would be a good choice as well...

[hmc2500]

The L3 switch is a WS-C3850-48T-S and Switch1 is a WS-C3850-12S (with fiber ports).

[Joseph W. Doherty]

"The L3 switch is a WS-C3850-48T-S and Switch1 is a WS-C3850-12S (with fiber ports)."

To my knowledge, different 3850 models have the same control plane support (which is what will support STP).

[Joseph W. Doherty]

As it appears you don't have any intentional loops, you don't need to "optimize" your network's effective L2 topology.

Further, assuming client ports are configured for port-fast, your root switch shouldn't have much to do.

So, I would lean toward using switch one, as it minimizes latency between root and other switches, but whether to use it, or a more "powerful" switch is somewhat six one way and half a dozen the other.  I.e. like @Georg Pauwen, I don't think in this case it matters much, but again, my personal preference, given the information you've provided, would still be to "prefer" using switch1.

PS:

Switch6 would be another candidate as it's only two hops from all the other LAN switches.  Switch1, though, is just one hop from the most switches.

[hmc2500]

Yes, portfast is configured on all the switches for end points. 

forgot to mention that we have about 5 vlans of which of course the interfaces are hosted on the L3 switch. 

[Joseph W. Doherty]

"forgot to mention that we have about 5 vlans of which of course the interfaces are hosted on the L3 switch."

Well also forgot to mention, a L3 switch hosting the gateway SVI often also is root bridge.  This too, often is done because such a switch is central to your network to minimize interswitch latency (to/from SVIs).

That said, again, you don't need to align L2 and L3.  In your case, it matters little, because of your topology, although depending whether your traffic flows (which can differ for L2 vs. L3), generally, you want to avoid hopping across switches you don't need to.

All 3850s are L3 switches, but, of course, feature usage depends on license on them.

Not yet mentioned, as an aside, if not using rapid-STP, you should vs. non-rapid-STP (Cisco default).

Lastly, as you have 5 VLANs, since Cisco supports per-VLAN-STP, you can have different root bridge placement for each VLAN.  Again, with your topology, doing so buys you very little.

[paul driver]

Hello

Switch 1 is the most central to the switching estate it has the majority of the switch's directly connected as such when stp converges  propagation for tcns would be to/from a central point also.