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For each OID referenced in the configuration file, MRTG creates the following graphs:
Daily graph—5 minute average data points with approximately 33 hours of data presented.
Weekly graph—30 minute average data points with approximately 8 days of data presented.
Monthly graph—2 hour average data points with approximately 5 weeks of data presented.
Yearly graph—1 day average data points with approximately 1 year of data presented.
To quickly create images by using the GD graphics library, go to http://www.boutell.com/gd
To select which dial OIDs to query when monitoring dial-up activity, see the OIDs listed in the
following tables:
Circuit utilization OIDs (Table 14)
Modem information OIDs (Table 15)
User information OIDs (Table 16)
Be cautious when polling network elements. Polling OIDs that retrieve large amounts of
data can cause CPU problems on a Cisco IOS device. For example, do not get the ARP
table, walk large portions of a MIB tree, poll the wrong OID too frequently, or get statistics
that have an entry for every interface. For example, a Cisco 7200 may have 10 interfaces;
whereas, a Cisco AS5800 may have 3,000 interfaces.
In this case study, the tools UCD-SNMP and SNMP Commander were used to inspect and understand
the MIBs. Based on this research, the network engineers at THEnet identified the OIDs in the following
tables to program in to MRTG.
To see the complete structure of the CISCO-POP-MGMT-MIB and CISCO-MODEM-MGMT-MIB,
go to the following URLs:
CISCO-POP-MGMT-MIB
http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/dialnms/popmgt.txt
CISCO-MODEM-MGMT-MIB
http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/dialnms/modemmgt.txt
Analog calls
CISCO-POP-MGMT-MIB
1.3.6.1.4.1.9.10.19.1.1.2
Active DS0s
CISCO-POP-MGMT-MIB
1.3.6.1.4.1.9.10.19.1.1.4
Call count
CISCO-POP-MGMT-MIB
1.3.6.1.4.1.9.10.19.1.1.1.1.7
The number of analog calls connected.
The total number of calls connected.
The number of calls that have occupied a
specific DS0.
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