Network Analysis

[Udir]

I have been asked at work to provide a detailed network analysis to evaulate the possibility of running VoIP.

I am going to use QOS, but we have several remote sites, and I am guessing that I need to evaluate the amount of traffic flowing over these lines, and how much of a particular type of traffic will be dropped.

The question is what do you recommend to evaluate traffic based on protocol, port, service, etc over the network?

Am I going about this the right way? Any other suggestions or recommendation would be appreciated.

 

[routerman]

What sort of WAN do you use, frame-relay, ATM etc.

Can your routers support NetFlow, this can give a lot of info on connections. To check for NetFlow support go on to a serial interface, and enter `ip route-cache flow ?' There is a memory overhead with this, so initially just add the ? to see if your IOS suports this option.

 

[Udir]

All of the WAN's are dedicated T1's. And yes the router does support Netflow. What do I read the Netflow with? Do switches support this option? How does one go about collecting this information and evaluating it? Thanks for the reply router man...

 

[dx1]

You can view the netflow with:
sh ip cache flow

To collect and graph the netflow info, you can use something like Cflowd and FlowScan. You can find more info about them with Google.

There are also 3rd party apps that will graph the netflow data. They cost money.

 

[Andyleates]

Does anyone know if I can just take the stats of my router, i.e.

Protocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec)
-------- Flows /Sec /Flow /Pkt /Sec /Flow /Flow
TCP-Telnet 1 0.0 1 40 0.0 0.0 15.1
TCP-WWW 132 0.0 31 105 0.0 2.4 5.6
TCP-other 1718 0.0 19 174 0.0 4.5 13.2
UDP-DNS 7 0.0 1 63 0.0 0.6 15.4
UDP-other 217 0.0 230 80 0.0 9.2 15.5
ICMP 30 0.0 1 57 0.0 0.0 15.5
Total: 2105 0.0 41 117 0.0 4.8 13.0

and work out percentages myself, rather than going through all the process of collecting the data with software, etc?

Andy Leates MCSE CCNA MCP+I

 

[routerman]

Andy,

If I'm looking at a specific problem on a customer site then I take the netflow stats, save to a text file and then import into excel, this way I can sort the data.

This can give me an idea of the communication paths and the amount of data transferred between peers, but is only useful for taking snapshots. It may help in ypur case, perhaps regular snapshots could be taken using a script of some sort?

 

[Andyleates]

Thanks for the answer. I just wanted to see if working out total bytes per protocol by multiplying bytes/packet by packets/flow and then multiplying that by the number of flows was going to give my a true picture...

Andy Leates MCSE CCNA MCP+I