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Network Design and Bandwidth/load calculation

I need to design the network for a campus having around 20 different location/buildings and these connect to the centralized data center where 6513 switches are working in VSS with 2T supervisor engine.

Access switches considered as 2960 and its a POE+ to support IP telephony and CCTV.

At distribution we are planning to use 3750 or 4500 depending on the load of the systems.i

Single mode fiber is used between distribution to core and L2 link between Access and Distribution is multimode and makes etherchannel of two redundant links

I need to calculate the load on the core switch when all the systems are active (Data,IP telephony,IPTV, CCTV,BMS)

Need some documents for bandwidth calculation based on the users of different systems and load on the core and distribution switch by considering trunk links as single and ether channel.

Lets say for example 1000 user for Data and 500 for IP telephony and 400 for other systems

(IPTV,CCTV,BMS). How the load calculation will be done on the distribution and core switch so that the network will not break down.



Everyone's tags (2)

Re: Network Design and Bandwidth/load calculation

Do you have any statistics about how much each of these devices utilize ?

If not it is hard to be specific as not all of these devices will be sending traffic at the same time at all times !

What you can do is consider cisco recommendation of having your uplinks oversubscribtion as bellow

20:1 access to distribution

4:1 distribution to core

Then make sure the core can handled the aggregated bandwidth

And consider 10g distribution to core

And using vss with MEC can help alot interims of more active links and increasing the uplinks available bandwidth

QOS is another important thing to consider to protect real time sensitive traffic during link congestion periods

Hope this help

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Hi Marwan,

Hi Marwan,

I am new to designing and learing mostly through this online support forms, can you please explain in brief what is this 20:1 access to distribution & 4:1 distribution to core

Thanks and regards

Community Member

Network Design and Bandwidth/load calculation

hi Fazal,

i dont have any answers regarding your question, but perhaps i want to share my experience.

in designing network, capacity planning is quite difficult, so normally we make design based on some assumptions, which those statistic numbers belongs to. so in the early page of my design proposal/presentation slide, i always write this assumptions.

but after it becomes production network, some variables are changing, for example the user behavior. how the user use their network defines the traffic characteristic.

and some times those assumptions that we made are wrong, then everybody blame the design or the designer

but for me, i always say to my self that there is no so called wrong design, its just that we fail to make some assumptions. and these assumptions should be made by the designer and the user.

happy designing


Community Member

Network Design and Bandwidth/load calculation

Thanks for the reply guys.

We are using VSS with 2T supervisor engine and each distribution switch has redundant link form core and its combined as MEC( multi chasis etherchannel)

I calculated the Bandwidth for all systems as per this calculation in mega bits.

IPTV        IPT          IPVS         Internet

20mb       0.25mb    10mb         2mb

lets say 48 port switch has 10 connections from each systems then total load on the access switch is  345 mb and 3750G-12S has the Bandwidth aggregation up to 16 Gbps through 10 Gigabit EtherChannel technology, 8 Gbps through Gigabit EtherChannel technology.

If i consider the 1 GB link between access and distribution then bandwidth aggregation is  8 gbps and it can  support around 20 access switches (2960 48 ports  POE+)

At the core switch i assume bandwidth is more enough to support all the distribution switches as per this statement "The Cisco Catalyst 6500 Supervisor Engine 2T is the next generation switching system that paves the way for 2-Tbps of switching capacity, scaling to 4 Tbps when deployed in a virtual switching system (VSS) configuration"

In this case what is the problem if i use 20 distribution switches and dont follow the rule 4:1 as the VSS support high switching capacity and bandwidth.

Randomly i selected the traffic of the IPTV,IPT,IPVS, and internet but is there any docuement which can be used.

For sure QOS are important when no of systems are working together specially voice and video.

Expecting reply on the above points and any suggestions and sharing of previous experiance.



Community Member

Network Design and Bandwidth/load calculation

hi Fazal, pls check your inbox.


Community Member

Network Design and Bandwidth/load calculation

Hi Handoko,

Please reply to your inbox mail.

Looking for your response


Network Design and Bandwidth/load calculation

you can use the suggested uplinks oversubscribtion ration with MEC uplinks using SUP2T and gonna be more than enough

you might need to consider 10G uplinks as desired

however make sure that the access switches meets the required amount of bandwidth/throughput of layer 2 siwtching


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