Maximum 10Gb Ethernet hops within a campus

[steve.blunt]

I have a customer who has engaged a third party to install OS2 single mode fibre across their campus, unfortunately the supplier has installed loops, within loops, in short the topology is a nightmare. There are two central data centres, but the vast majority of fibres are daisy chained through remote cabinets, all fibres are installed in single lengths e.g. from core 1 to cab A then a separate length to cab b, then to cab c etc, eventually the last cab in the sequence connects to the secondary computer room. Some of these links have up 12 hops! 

The customer is expecting a 10Gb back bone between all cab, the number of passive fibre patching links required to implement a VSS deployment blows the loss budget for the fibres, deploying distribution nodes around the ring (say Cat4500X) would become expensive as so many are required. I will be utilising Cat 6880 as the campus cores, currently there will only be 20 direct attach 10Gb interfaces per switch (one per data centre).

The customer is unlikely to be able to accommodate a complete layer 3 routed access migration, but will discuss. So that leaves me with the option of actively repeating 10Gb links between cab to provide connectivity to the cores daisy chain style (not exactly best practice!).

So can I take advice on the following please?

The campus will have approximately 200 access layer switches deployed over 60 remote cabs

Longest daisy chain is 12 hops, average is 6

Applications will include IPT, room based Video conf, MS Office etc

There will be over 8000 hard wired and 600 wireless (Cisco 2702i and 8500 WLC) clients 

1. If using a layer 2 trunked / pruned VLAN access layer approach, using say two MST instance (one for even VLAN numbers the other for odd) are there any real-life recommendations for the maximum number of active repeated hops?

I have looked at easy virtual network (EVN) but am worried about the scalability and lack of reference sites

2. I'm evaluating the Catalyst 2960XR and 3650 access switches, both support the required feature sets. The 2960XR has a lot less memory and a single core CPU when compared to the Cat 3650, based on the potential traffic which may flow through a switches up-link port to reach a core then the choice of access switch is important. I have been advised not to worry too much about the memory and CPU as port forwarding does not impact on CPU as its primarily an ASIC based task

Any advice greatly welcome!

[Leo Laohoo]

1. If using a layer 2 trunked / pruned VLAN access layer approach, using say two MST instance (one for even VLAN numbers the other for odd) are there any real-life recommendations for the maximum number of active repeated hops?

I have looked at easy virtual network (EVN) but am worried about the scalability and lack of reference sites

I have a question, would it be possible if you can run a very, very long patch cord from your core switch to the main fibre lean-in?  I really don't appreciate so many re-patching loops.  Not only does this provide a nightmare when you've got a failure with the line but you've also taken out "space" in the FOBOT.  

2. I'm evaluating the Catalyst 2960XR and 3650 access switches, both support the required feature sets. The 2960XR has a lot less memory and a single core CPU when compared to the Cat 3650, based on the potential traffic which may flow through a switches up-link port to reach a core then the choice of access switch is important. I have been advised not to worry too much about the memory and CPU as port forwarding does not impact on CPU as its primarily an ASIC based task

3650 and 2960X are two seprate beasts.  All Cisco Catalyst 2K and 3K switches will be stackable.  The question is just the stacking speed.  

3650 is a Layer 2/3 switch with capacity to become a wireless LAN controller.  2960X/XR is a Layer 2 switch with some limited Layer 3 capabilities.   Catalyst 3K switches can support EEM but Catalyst 2K switches will never support EEM.  

For obvious reasons, prices will be a significantly different. 

To choose one or the other will depend entirely on your future planning and your current budget.  If you want to do routing-to-the-floor then getting a model that can do very good routing speed is a better.

NOTE:  Since you're talking about Instant Access, have you seen the new model of 3650CX?   A new model, the WS-C3560CX-12PD-S, will be the first of it's kind as a "hybrid":  This particular model can operate either as a traditional Cisco IOS or Instant Access.