Nearly every network engineer I work with is either looking for a way to monitor their bandwidth or ways to improve how they monitor their bandwidth usage. So, popularity wins out this week and the next couple of posts will be a series on implementing bandwidth monitoring.
Why monitor bandwidth usage?
We each have our reasons, here are some of mine:
1. When the network slows, lots of people call and complain, and I don't like that
2. Need to have data supporting when an upgrade to the T1 line is necessary and validation that we are getting the service we have paid for
3. Helps to understand what servers are being used heavily and when the load should be split into multiple servers
4. Lets me identify high bandwidth consumers and adjust the network topology keeping the key users close to their end systems
5. Allows me to locate end users who are downloading high volumes of data and request they stop during sensitive times (executive webcasts etc…)
Getting started: SNMP enable your network
To effectively monitor bandwidth usage it requires that you have a method of accessing the bandwidth consumption statistics for each device. SNMP is the industry standard and works with all major brands of networking devices, server and workstation operating systems. It uses a software agent installed on each device and a collector type system to aggregate and report the data. With SNMP you will be able to collect bandwidth data such as utilization % for each interface, total packets, discards and more. Here is a screenshot of a typical interface display for an SNMP enabled device:
To retrieve this information on a device, you will need to set a community string (aka password) that your monitoring system will use when retrieving the bandwidth statistics. At the bottom of this article are the steps to enable SNMP on Windows and Cisco devices.
For more overview information check out these website links:
http://www.dopplervue.com/bandwidth.php and the tutorial at http://www.dopplervue.com/tutorials_show.php?what=Managing_Bandwidth.
The next blog post will discuss monitoring systems that can gather this data, what to do with the information, alerts and rules that can be set and common reports that you will want to use for bandwidth monitoring.
Enabling SNMP on a Windows System
Windows 2003 and XP
1. In the Control Panel, click Add Remove Programs.
2. In the left pane, click Add/Remove Windows Components.
3. Select the Management and Monitoring Tools checkbox and click Details.
4. Select the Simple Network Management Protocol checkbox, click OK, and then click Next.
5. If prompted, insert the Windows 2003 or XP disc to finish the setup.
1.In the Control Panel, click Programs and Features.
2. In the left pane, click Turn Windows features on or off.
3. Select the SNMP Feature checkbox and and click OK.
On a Windows system, you must configure security for the SNMP service by adding a community name(s) and permissions to a list of communities that can send it SNMP requests. This is known as a "community string":
1. In the Control Panel, click Administrative Tools, and then click Services.
2. Right-click the SNMP Service, click Properties, and then select the Security tab.
3. In the Accepted Community Names pane, click Add.
4. You may accept the default community rights, and then enter a community name (case sensitive). Click Add.
5. Select Accept SNMP packets from any host, and then click OK.
This ensures all SNMP packets from all SNMP hosts belonging to any community listed in Accepted community names are processed. No SNMP packets are rejected on the basis of the host name or IP address of the source host or the list of acceptable hosts.
6. Ensure the SNMP Service is selected and click Restart the Service to initiate the changes.
Enabling SNMP on Cisco Devices
Log in to the router and enter configuration mode: Router#configure terminal
1. Enable SNMP on the router (note that "public" and "private" are for example purposes):
Router(config)#snmp-server community public RO
Router(config)#snmp-server community private RW