Network Design Scenerio

[abbas.ali]

In a typical design, we go with fixed port switches such as Cisco 2900/3560/3750 series switches for the IDFs, and chassis based switches such as 6500/4500 for the MDF.  However, I have a customer who would like to do it otherway around.  Since his requirments are more in IDF than MDF he would like to go with Cisco 4500 series switches for his (3) IDFs and Cisco 3560 or 3750 series switches in the MDF as core swiches to connect server farm (Virtual and Phyiscal) and also downlink to Cisco 4500 IDF switches.

How do I make sure that we won't run into any oversubscrition or bottle neck issues with this soution.

Is it uncommon to design this way meaning chassis based switches in IDF and fixed port switches in MDF as core?

Thanks,

[Jon Marshall]

Abbas

It is not that uncommon to use modular chassis in the IDF if you need a lot of port capacity for example. I have used 4500s before but they were connecting to 6500 distro/core switches.

If the customer is think of using 3560 or 3750 then make sure they go with 3750 which gives you stacking plus the ability to run MEC (Multichassis Etherchannel) from the your IDF switches, assuming L2 etherchannel trunk uplinks to the MDF switches.

As for subscription there is no easy answer to this because it's not clear what specific version of the devices they are using. For example the 4500 with SupV can support 6Gbps per slot. With sup6 that goes up to 24Gbps. With Sup7 up to 48Gbps per slot so you can see purely at the IDF level there can be a huge difference.

Again the 3750 has 3 variants ie. 3750/3750E/3750X and each has different switch fabrics and throughput figures so again it depends on what you are looking at.

What you need as with any design is work out how much bandwidth you will be getting from the IDFs in total and then together with your oversubscription ratio work out which devices you need in the MDF. It may be you can use 3750s, but it may be that you need to recommend a modular switch.

Jon

[abbas.ali]

Thanks Jon!

[Leo Laohoo]

I don't recommend using the plain 3560/3560G or the 3750/3750G.  I'm expecting Cisco to announce the end-of-sale of the 16 mb flash version soon.

[Joseph W. Doherty]

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Posting

As Jon has already noted, there are some major performance differences between 3560/3750 generations.

Would not recommend original series for any but the smallest core deployments.  Later gen (E or X series) devices certainly have the raw performance.

As Jon also mentioned, stacking is good for MEC.  However, although a single later gen 3560/3750 is great, you can bottleneck on the stack ring.  This is were a 4500 can be better vs. a large number of members within the same stack as it offers a fabric between line cards.

If you intend to stay with just a non-stacking device, like the 3560, you might also want to review the 4900 series too.