Could a pair of 3850 make a good redundant core in a small business?

[#1]

Hi all, our core today is a large stack of 3750's.  Some are X's some are the 3750g v2's, and some regular v2's (100mbps).  Since were a small business we have the majority of our HQ accessable by ethernet so the core is also the access layer for many of the endpoints, except for a third floor which is too far so fiber is sent to that closet to another group of 3750x's and v2's in a stack.

We also have 3750x's at remote offices which are all connected through 2901 routers and metro-e solutions (carrier depending on location).

Because the 3750 stack in the HQ has most things plugged into it (servers, wan links, asa handoffs, etc...) if something were to happen to it, we would be SOL.

Could breaking out this core functionality and moving the routes and default gateway to a pair of 3850's make sense?  We want something redundant to the point where one switch could go down, either planned (like for an IOS upgrade or configuration change) or unplanned (god forbid a failure or misconfiguration) we could still have some sort if not all possible network connectivity.

So breaking out the current, collapsed core I guess I will call it, where everything is uplinked to a pair of 3850's, and all the routing is on the 3850's, could they be configured with active/standby or active/active where if one goes down or looses power, the core network is still functioning?  Would 3850's make a good candidate for a small business?  Do 3850's support SFP+ ports for 10gbe SFP+ modules (fiber or twinax)?  Would a 5508 WLC controller be redundant since I see a feature of the 3850 has to do with CAPWAP processing?  Or would we keep our existing 5508 WLC and 3500 series LAP's?

[devils_advocate]

It does sound like something needs to be done, the 3750 stack seems to be the 'Core' of the network and losing it would be a disaster. Obviously the stack feature of the 3750's means you have a level of 'redundancy' but that is meaningless if you only have single uplinks for the remote sites.

Depending on your budget, you have a few options really.

The 3850's are aimed at being access switches because all the built in ports are 1Gb. They can use 10Gb modules which provides up to four 10Gb ports per stack members. 

If it were me, I would be looking at a pair of 4500x switches in a VSS arrangement as these support 1Gb or 10Gb SFP's. 

If you are looking to move towards a 10Gb nework in future, the 3850 switches are going to limit you.

In terms of wireless, how many AP's do you need to support?

The 3850's do have a built in WLC but you need to purchase licences for each AP and I remember reading somewhere that the AP's have to be plugged into the 3850's for them to work. I could be wrong about this so am happy to be corrected. 

[Joseph W. Doherty]

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Posting

Well, one issue you have, which you might not realize, although you can mix StackWise and StackWisePlus 3750s in the same stack, mixing them causes the StackWisePlus capable units to yield much of the benefits of StackWisePlus.  So, without even jumping into newer units, splitting your existing stack into a StackWise and StackWisePlus stacks, might offer some benefits.  (Keep the high bandwidth devices connected to the StackWisePlus stack, and low bandwidth devices to the StackWise stack.  MEC between the two stacks.)

Also be aware, the 3750 architecture provides 2 MB of RAM buffers per 24 copper ports or to its module ports.  So where you connect busy ports is important too.

For remote sites that only have a single link to your HQ, if possible, "pre-define" another port on a different stack member as a cold backup.  If the stack member fails, hosting the active remote site port, you would only need to repatch that link to the alternate port.  (BTW, one way to do this for routed port, convert original port to a switch port, add the backup port to the same VLAN, and dedicate a VLAN for the p2p.)

Regarding the 3850s, they are much like a new generation of 3750s.  I think they too would be suitable for a small core, but even if you go with those, I would still advise splitting your StackWise vs. StackWisePlus units.

I'm not familiar with their embedded WLC, but I understand the 5508 to handle more.  I.e. I believe the embedded WLC is for smaller WLAP deployments.

Devils_advocate's suggestion for using a pair of 4500X, in VSS, is worthwhile, but likely (much?) more expensive, and VSS is more for dual links everywhere.  The stacks better support single links.