Managing Your OSPF Network

Previous Table of Contents Next

Monitor polling applications are included with HP Openview and Netview 6000, and can be configured with Sun Net Manager. You can customize monitor polling with add-on products like NetLab’s Nerve Center. The individual data points returned from monitor polling are not important. The monitor polling application analyzes the data points to generate alarms.

Threshold Polling

Many problems show up first as increased error conditions. They might eventually become hard errors, or they might be “phantom” problems that come and go. Threshold polling detects these escalating error conditions and acts before performance is severely impacted. To implement threshold polling, first decide for which MIB variables to poll, and then add other MIB variables as appropriate.

After you have decided on the threshold MIB variables, establish baseline values for these variables by starting a poll process on the MIB variables. After some period of time (for instance, one week), review this data to determine what values are “normal” for your router. Then, use these normal values to determine what the highest acceptable values, or thresholds, would be. A good rule of thumb is to set your thresholds 10-20 percent larger than the maximum values.

The threshold values for any particular MIB variable may be applied uniformly across all routers, or they could be customized for groups of routers that have similar characteristics (like core, distribution, and access).

You also need to decide on appropriate notification for threshold violations. These violations are not hard errors—immediate notification is unnecessary. Logging all threshold values and reviewing them daily usually works well. It is important to investigate repeated threshold violations, to determine if a problem has occurred that can be corrected or if your threshold values are too low.

Performance Polling

Performance polling gathers data over time that can be analyzed to determine trends and to aid in capacity planning. First, determine what MIB variables to poll for. One of the following sections, “Recommended MIBs for Data Collection,” has some suggestions for variables that would be useful for Cisco routers.

For performance polling, individual data points are stored intermittently on the polling machine. Depending on the polling mechanism you are using, the data could be in either a raw format (the default for Openview and Netview 6000), or a relational database. CiscoWorks uses Sybase.

To keep the data manageable, aggregate the raw data periodically, and store it in another database or datafile for future reporting. Keep the raw data for a period of time for backups, but purge this data eventually and keep only the aggregate data. Use this aggregate data to produce reports that will be periodically reviewed to determine trends and patterns.

Performance Polling System Example

Individual MIB variables are grouped together in a series of polling groups. Each group is polled every five minutes and the data is stored in Sybase databases by poll group names. Every morning at 12:01 AM, the raw data in Sybase is aggregated into minimum, maximum, and averages for each hour and stored in another Sybase database (the user has written SQL programs to accomplish this).

Every Saturday morning at 1:00 AM the individual raw data points are purged from the database for the previous week. On the first day of each month, the hourly min/max/avg data is aggregated into daily min/max/avg data and stored in another database. A series of reports are generated from both the daily and hourly data for review at the Capacity Planning meeting on the first Tuesday of the month. After the reports are produced, the data from the hourly database is archived to tape.

The following section examines the MIBs Cisco recommends for use within your network.

Recommended MIBs for Data Collection

For overall router performance, the recommended MIB is as follows:


For all interfaces, the recommended MIB is as follows:    ..mib-2.interfaces.ifTable.ifInErrors    ..mib-2.interfaces.ifTable.ifOutErrors 

For serial interfaces, the recommended MIB is as follows:

    .. cisco.local.lifTable.locIfCRC    .. cisco.local.lifTable.locIfAbort    .. cisco.local.lifTable.locIfFrame    .. cisco.local.lifTable.locIfCarTrans    .. cisco.local.lifTable.locIfOverrun 

For Ethernet interfaces, the recommended MIB is as follows: 

For Token Ring interfaces, the recommended MIB is as follows (from RFC 1231):

    dot5StatsLineErrors    dot5StatsBurstErrors    dot5StatsACErrors    dot5StatsAbortTransErrors    dot5StatsInternalErrors    dot5StatsFrameCopiedErrors    dot5StatsTokenErrors    dot5StatsSoftErrors    dot5StatsSignalLoss    dot5StatsFreqErrors 

For FDDI interfaces, the recommended MIB is as follows (from RFC 1512):

    snmpFddiMACLostCts    snmpFddiMACErrorCts 

Accessing Cisco MIB Files

You can obtain the files that describe the MIBs supported by Cisco products using anonymous FTP or the World Wide Web to access Cisco Connection Online (CCO), formerly Cisco Information Online (CIO).

Via FTP, use the command. Log in with the username anonymous, and enter your e-mail name when prompted for the password. Use the cd pub/mibs command to go to the directory that contains the MIB files, and then issue the get README command to obtain the README file containing a description of the Cisco Systems public MIB area. To determine the MIBs supported for each Cisco product, go to the supportlists subdirectory where you will find directories for all Cisco products. Refer to the supportlist.txt file in each directory, as necessary, to determine the MIBs supported on that platform, by Cisco IOS release, and the location of the desired MIB file. Cisco IOS MIB files are in the v1 and v2 subdirectories. You can then use the FTP command get mib-filename to retrieve the MIB file.

Previous Table of Contents Next

OSPF Network Design Solutions
OSPF Network Design Solutions
ISBN: 1578700469
EAN: 2147483647
Year: 1998
Pages: 200
Authors: Tom Thomas

Similar book on Amazon © 2008-2017.
If you may any questions please contact us: