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New Member

Bandwidth monitoring, throughput and broadcast storm question

Hello all- This is my virgin post on the site and I am fairly new in their field, so please be kind and patient.

Here is what I am currently working on; any help or advice would be greatly appreciated.

(1) Catalyst 2960 48-port switch and (1) SGE 2010P 48-port switch

Base internet speed: T1 (1.544Mbps)

While I am aware of the fact that the T1 is in desparate need of an upgrade, that matter is out of my hands.

What I am looking at are ways to manage the bandwidth more efficiently.

2960 switch-28 of the ports are in-use

2010p switch-42 ports are in-use

-One of the simplest things I thought of trying was to set a threshold on the broadcast, unicast and multicast traffic.

I am a little uncertain though as to the ways in which I can monitor that traffic (cannot use third-party software or netflow; strictly via command line)

-I did a "show processes cpu" on the 2960 the output was as-follows:

Switch>sh processes cpu

CPU utilization for five seconds: 12%/1%; one minute: 12%; five minutes: 12%

PID Runtime(ms)   Invoked     uSecs   5Sec   1Min   5Min TTY Process

Additionally, I checked and STP is functional on all company switches and storm control is disabled on all.

How should I proceed? And, is this juice even worth the proverbial squeeze? Like I said, the T1 will be upgraded soon, but right now I am only looking at things that I have control over.

Thanks,

  • LAN Switching and Routing
8 REPLIES
Super Bronze

Bandwidth monitoring, throughput and broadcast storm question

Disclaimer

The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author  has been advised of the possibility of such  damage.

Posting

What specific bandwidth do you think you need to better manage?  For only two switches, it's unusual you would need to do anything beyond perhaps increasing the bandwidth between the two switches with an Etherchannel or perhaps an Etherchannel to a particularly active host or hosts.

New Member

Bandwidth monitoring, throughput and broadcast storm question

There are actually (8) switches (all strictly Layer 2) in the network. I am currently looking at the two aforementioned switches because they are the two with the highest amount of used ports.

Is limiting or essentially pruning (setting a threshold) the broadcast, multicast and unicast traffic that the 2960 and 2010p are processing going to have any effect on the bandwidth?

My thought was that broadcasts could be clogging-up some of the available bandwidth (I know not much).

I realize that I am very limited in what I can do because of the base speed is a T1, but I am looking for ways to improve traffic flow.

Any suggestions are appreciated. I am fully aware of the topics mentioned in the disclaimer as well.

Many thanks,

Gold

Bandwidth monitoring, throughput and broadcast storm question

how is all this connected? Are the two switches using the T-1 for internet access ?

can you configure rmon on the 2960? It takes some understanding of SNMP and mib objects,

New Member

Bandwidth monitoring, throughput and broadcast storm question

Yes, the switches use the T1 for internet access.

I am unfamiliar with configuring rmon. I know what it is, but I am not sure exactly how to configure and setup.

Super Bronze

Bandwidth monitoring, throughput and broadcast storm question

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

Posting

Number of ports being used per switch can mean very little.  Newer switches often support wire-speed between all ports.  For those, often the performance issue is more with per port bandwidth.

Normally, you only set threshold controls to engage for abnormal levels, but even when you have abnormal levels, there still often the "normal" traffic too which is adversely impacted by a threshold settings.  I.e. you use these setting to avoid complete network meltdown, but often still leaving a very bad performing network.

With eight switches, you might be borderline on breaking into a couple or L2 domains and route between them, but again I would look at inter switch bandwidth utilization and physical topology (ideally 7 switches connect to "backbone" switch).

Regarding the T1, hopefully you have a router that manages it.  For Internet FQ outbound is often good enough (vs. doing anything more complex).  Inbound (i.e. from the Internet) is often a problem unless you can control the far side's egress.

New Member

Bandwidth monitoring, throughput and broadcast storm question

Thanks Joseph! If I am understanding you correctly, you are saying that I am trying to do something (storm control) that is going to have little to no effect on the overall performance of the switches....right? And, I should be instead looking at Inter-switch bandwidth utilization and the physical design setup (topology) for bottlenecks and/or bandwidth utilization improvement.

Yes, there is a T1 managed by an edge router. All interconnected switches are fiber backbones.

Thanks for the responses.

Super Bronze

Bandwidth monitoring, throughput and broadcast storm question

Disclaimer

The      Author of this posting offers the information contained within this      posting without consideration and with the reader's understanding   that    there's no implied or expressed suitability or fitness for any    purpose.   Information provided is for informational purposes only  and   should not   be construed as rendering professional advice of any  kind.   Usage of  this  posting's information is solely at reader's own  risk.

Liability Disclaimer

In      no event shall Author be liable for any damages whatsoever    (including,   without limitation, damages for loss of use, data or    profit) arising  out  of the use or inability to use the posting's    information even if  Author  has been advised of the possibility of   such  damage.

Posting

Correct.

New Member

Bandwidth monitoring, throughput and broadcast storm question

I agree, you should investigate the links between the switches for usage.  There are a number of free tools that make it easy to monitor this as long as snmp is configured on the switch.  One I have used in the past is Opmanager, it has a free 10 device license.

Are your users actually complaining about speed?

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