What is the average normal number of broadcast and multicast of a middle size network

[swadeshmohanty]

Hi,

How to findout, What is the average normal number of broadcast and multicast of a middle size  network ?

Here is the command-line interface sequence to view counters

show interfaces counters ethernet 1/12

But, How i confirmed that this is the normal multicast or broadcast in my network ?

Please suggest me.

Thanks

Swadesh

[Peter Paluch]

Swadesh,

I do not think there is any universal figure or a recommendation what is the percentage of broadcast/multicast traffic in a network. The amount of such traffic strongly depends on the applications used in such a network. For example, in old Windows NT-style or Novell 2.x/3.x networks, the amount of broadcasts is significantly larger than in today's networks simply because those applications were built to use broadcasts to discover/announce their presence. A network using a video IP application is certainly going to devote a significant portion of its bandwidth to the multicast traffic but then again, the real amount depends on the codec being used, and so on.

What I am trying to say is that it is impossible to give a universal, general estimation of how many broadcasts are "good" and how many are "bad". My personal recommendation is that it is not that important to care about the amount of multicast/broadcast traffic until the network is operating properly. Estimating the normal and abnormal thresholds of multicast/broadcast traffic for your network would require a prolonged baselining to create a reliable statistical base.

Best regards,

Peter

[swadeshmohanty]

Thank you very much Peter.

So we conlude that, There is no such universal number.

All that matters is:-

The level of broadcasts using excessive CPU resources on any connected device.
The user traffic getting through sufficiently unimpeded.

Worry about the rate of broadcasts / multicasts arriving at a device.
If it generates too much load on the worst case device, then it is too high

Suppose, one of our client Network has;

50 computers

Some Windows and Redhat Linux servers

Some standard services like DNS, wins, dhcp like this

All of the Windows servers based on vmware virtulization.

Every computer or server is connected to managed switches.

His network seems healthy.

Can you please tell me . What is the average number of unicast/broadcast/multicast of that network according to the switch reports.

Please suggest me

Thanks

Swadesh

[Peter Paluch]

Hi Swadesh,

I believe you have summarized it very nicely. Yes, all that matters is that the network or device operation is not negatively influenced by the amount of broadcasts and multicasts in that network.

Regarding your question about average numbers of packets of different type - I am sorry but I really can not provide any absolute numbers, and that is what I tried to explain in my previous answer. It is only my very rough guess that a network like yours should not contain more than 5% of broadcasts in relation to the overall amount of traffic.

I would say here: "If it ain't broken, don't fix it"

Best regards,

Peter