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New Member

How to measure how many bandwidth used in the network via network switch?

Hi,

I’m planning to install a brand new Cisco firewall as follows.

Current Design

Switch A ------ Switch B

Proposed Design

Switch A --- New Firewall --- Switch B

In order to determine which model, I need to know how many traffic/bandwidth on the network. As example, if the bandwidth used in the network is about 150 - 300 Mbps, then we can use ASA 5510. But if more bandwidth used, then higher model is needed such as ASA 5520 (Maximum firewall throughput 450 Mbps).

http://www.cisco.com/en/US/products/ps6120/prod_models_comparison.html#~mid-range

Someone told me this can be done by “sh int” command on the switch, but I’m not sure the right way to do it/to read the output.

As example, output of sh int below shows that the bandwidth is 10000 Kbit. Is this the one that I should look for?

Router# show interfaces

Ethernet 0 is up, line protocol is up

Hardware is MCI Ethernet, address is 0000.0c00.750c (bia 0000.0c00.750c)

Internet address is 10.108.28.8, subnet mask is 255.255.255.0

MTU 1500 bytes, BW 10000 Kbit, DLY 100000 usec, rely 255/255, load 1/255

Encapsulation ARPA, loopback not set, keepalive set (10 sec)

ARP type: ARPA, ARP Timeout 4:00:00

Last input 0:00:00, output 0:00:00, output hang never

Last clearing of "show interface" counters 0:00:00

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

Five minute input rate 0 bits/sec, 0 packets/sec

  Five minute output rate 2000 bits/sec, 4 packets/sec

     1127576 packets input, 447251251 bytes, 0 no buffer

     Received 354125 broadcasts, 0 runts, 0 giants, 57186* throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     5332142 packets output, 496316039 bytes, 0 underruns

     0 output errors, 432 collisions, 0 interface resets, 0 restart.

http://www.cisco.com/en/US/docs/ios/12_3/interface/command/reference/int_s3g.html#wp1138804

Please let me know if you need more info. Thanks in advance.

12 REPLIES

Re: How to measure how many bandwidth used in the network via ne

Http://cacti.net

Sent from Cisco Technical Support iPad App

New Member

How to measure how many bandwidth used in the network via networ

Thanks Andrew for your prompt reply. Cacti require some configuration/installation. Is it possible to use available command on the Cisco Switch without using any 3rd party monitoring tool?

Re: How to measure how many bandwidth used in the network via ne

Hello Adam,

Depends on the cisco model you are using. You can try netflow, below a video for you to see.

www.youtube.com/watch?v=KujLCfW2V8w

Thanks

Vivek

New Member

Hi Vivek,

Hi Vivek,

I think on your formula one Zero is missing from 100,000,000. I believe this should be 1000000000. Reason is, as you mentioned above

1 Gbps          =  100,000,000,0 bps

If we do this in a different way on your interface output

3000 bits per seconds in kbps = 3kbps

3000 bits per seconds in kbps = 4kbps

3 + 4 = 7kbps

1G = 1000000kbps ( MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec)

formula

7/1000000 x 100 = 0.0007%

Please correct me if I am wrong

Re: How to measure how many bandwidth used in the network via ne

You can configure MRTG / Cacti / Solarwinds bandwidth monitor. MRTG & Cacti are freewares, solarwinds has a 30 day trial version. My suggestion would be solarwinds.

Thanks

Vivek

New Member

How to measure how many bandwidth used in the network via networ

Thanks Vivek, I really appreciate it. However, these solutions are not for me as I don’t have a write access to the switches & can’t configure additional tools on the network. But I do have read access to the switches and use any available command on it.

I did a quick google on this issue and found similar solution here.

How to Check Bandwidth usage on router ?

http://answers.yahoo.com/question/index?qid=20070910043818AAaS2Lr

So, I’ve performed “sh int Gi0/1” in 5 minutes interval and have the following outputs.

sh clock

7:47

7:52

sh int Gi0/1

...
5 minute input rate 3000 bits/sec, 3 packets/sec
5 minute output rate 4000 bits/sec, 4 packets/sec
     1754961 packets input, 383416613 bytes, 0 no buffer
     Received 515250 broadcasts (152537 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 515250 multicast, 0 pause input
     0 input packets with dribble condition detected
     1835485 packets output, 295200516 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

...
5 minute input rate 2000 bits/sec, 3 packets/sec
5 minute output rate 3000 bits/sec, 3 packets/sec
     1755859 packets input, 383580756 bytes, 0 no buffer
     Received 515457 broadcasts (152599 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 515457 multicast, 0 pause input
     0 input packets with dribble condition detected
     1836470 packets output, 295363529 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

Quick comparisons between these two outputs are as below. Can I determine how much bandwidth used in the network based on this info? Please advise.

ITEMS

BEFORE

AFTER 5 MINUTES

DIFFERENCE

5 minute input rate

3000

2000

-1000

5 minute output rate

4000

3000

-1000

packets input

1754961

1755859

898

bytes

383416613

383580756

164143

broadcasts

515250

515457

207

multicasts

152537

152599

62

packets output

1835485

1836470

985

bytes

295200516

295363529

163013

Re: How to measure how many bandwidth used in the network via ne

The formula to calculate utilization is

Utilization (U) Percentage = (Throughput/Data Rate) x 100

For example as below

5 minute input rate 3000 bits/sec,

5 minute output rate 4000 bits/sec,

Utilization Percentage (input) = (3000 / 100,000,000) x 100 = ?

Utilization Percentage (output) = (4000 / 100,000,000) x 100 = ?

Utilization Percentage (total) = [(3000 + 4000) / 100,000,000] x 100 = ?

I was too lazy enuff to calculate the stuff But that's the formula you can use. Those input/output rate is based on your screenshots.

Hope this helps.

Thanks

Vivek

New Member

Re: How to measure how many bandwidth used in the network via ne

Thanks Vivek for the info. I’ve learned something new today

And don’t worry about the calculation as there is a reason why spreadsheet as excel or calculator is created.

Here is the answer for that. But I was wondering where do you get the value of “100,000,000”

Utilization Percentage (input)

0.003

Utilization Percentage (output)

0.004

Utilization Percentage (total)

0.007

Re: How to measure how many bandwidth used in the network via ne

Thanks for that But i need to seriously learn to calculate lol..

Have a great time.

Thanks

Vivek

New Member

Re: How to measure how many bandwidth used in the network via ne

Utilization (U) Percentage = (Throughput/Data Rate) x 100

Ah, I’ve overlooked the formula given above. Does it mean value of “Data Rate” is always 100,000,000?

I’ve just discussed about this matter with my friend and he said “input rate” is enough to determine the bandwidth used in the network. So, obviously Cisco ASA 5505 is just nice as it can support up to 150 Mbps throughput while the throughput on the network just 3000 bits/sec. Is that true?

Cisco ASA 5500 Series Model/LicenseCisco ASA 5505 Base /
Security Plus
Cisco ASA 5510 Base /
Security Plus
Cisco ASA 5520Cisco ASA 5540Cisco ASA 5550
Product Image
(click to enlarge)
Network LocationSmall Business, Branch Office, Enterprise TeleworkerInternet EdgeInternet EdgeInternet EdgeInternet Edge, Campus
Performance Summary
Maximum Firewall throughput150 Mbps300 Mbps450 Mbps650 Mbps1.2 Gbps

http://www.cisco.com/en/US/products/ps6120/prod_models_comparison.html#~mid-range

New Member

Re: How to measure how many bandwidth used in the network via ne

Hi,

maybe I missed that, but what kind of switches are we talking about (at least what kind of ports)?

If you use the 'show interface' command and read the 5min rates over the busiest times (for each 10 minutes or so)

you should at least get a feeling about your bandwitdth requirement.

Regards,

Michael

Re: How to measure how many bandwidth used in the network via ne

No, your data rate is dependent upon the interface you have. That one was for Fastethernet interface.

100 Mbps      = 100,000,000 bps

1 Gbps          = 100,000,000,0 bps

You need to consider capturing the utilization during your peak usage hours which will provide you an idea of average traffic you receive on the interface.

AFAIK, to measure the throughput you need to consider input/output rate as it's bidirectional. Don't get confused with speed & throughput, they are two different things. Maximum firewall throughput isn't speed of the interface. What that says is a maximum traffic of 150Mbps could be handled by the firewall (which is actually from inside & from outside).

Hope i tried clarifying.

Thanks

Vivek

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