9800 interface seizing

[jmecklenburg]

Hi Guys.

I need to know how to calculate the seizing for the interfaces in a C9800, for example if I have a c9800 in central switching whit 1Gbps uplink for 20 AP an 100 user i'm fine but if I have 200 AP whit 1000 users the requieremnt for the interfaces it's not the same.

How to calculate this interfaces?

regards.

[Rasika Nayanajith]

Oversubscription is normal for this scenario. Even if you think each AP is capable of generating 1Gbps throughput, in most of practical scenarios average wire data throughput is much less than 1Gbps. In that case, even if you got 200 APs total throughput will be much less than 1Gbps overall. Here is an example of a 9800 with 300 APs (yes it all depends on what users do with WiFi)

If it is FlexConnect design, then for WAN links you need to have minimum bandwidth ~24kbps per AP for CAPWAP control (assume data traffic will locally switch at branch). Below table summarize cisco recommendations

HTH
Rasika
*** Pls rate all useful responses ***

[jmecklenburg]

I understand, but I think should be a best practice or recommendation to calculate the bandwidth in different scenario.

[Rasika Nayanajith]

Very difficult to calculate it. Based on my experience 500-1000APs, 1Gbps is sufficient. If you have more than 1000APs, then having a 10Gbps link to your WLC makes sense. If you have the option of go with 10Gbps (physical port available on your WLC & SW) go with it.

Here are some real-life stats from a WLC (5520) with 600APs. Past 24hrs vs past 30 days (throughput in means client upload, & throughput out means client download). Even if you look at max-bit rate values are below 1Gbps mark.

HTH
Rasika
*** Pls rate all useful responses ***

[patoberli]

In my case, I had about 1500 clients online spread over about 250 APs. They were students and we had a fast and open Internet connection. But still, the 5 minute average was very rarely > 1 Gbps.

My suggestion is to attach at least two cables to the WLC (for redundancy if possible, needs a Switch Stack oder VPC/VSS) with Etherchannel active. That would give you at a minimum 2 Gbps, typically more than enough bandwidth. 

[Rich R]

And this is a WLC with 3000 APs - last month:

(for some reason image upload not working for me so attached!)

[jmecklenburg]

Right now I have one c9800 with a port-channel LACP with 2Gbps BW the average is over 500Mbps in one interface and 200Mbps in other so I need to knowif they any math fot the interfaces.. but apparentli is not.

[patoberli]

There isn’t really any math for this, assuming you meant the word math.

It really depends, do you have 1000 Youtube 4k users or do you have 1000 email users. While the first ones will completely use all the available bandwidth, the latter ones will just use 200 Mbps when they attach some pictures.

So it really depends on what your users are using, nobody knows this better as you yourself

About your statistics, so you have now peaks up to 700 Mbps spread over 2x 1 Gbps links. In this case I’d probably add another two 1 Gbps links, or upgrade to 10 Gbps if the hardware allows. That should provide enough bandwidth for the next few years.