Extensible SNMP Agents

1
Extensible SNMP Agents

• Monitoring network and system functions within an
  SNMP polling framework
• (Related to Essential SNMP 2nd Ed.,Chapter 10

2
Private Enterprise Numbers

• iso.org.dod.internet.private.enterprise
  (1.3.6.1.4.1)
• http//www.iana.org/assignments/enterprise-numbers
  
• 0 Reserved 1 NxNetworks
• 2 IBM 3 Carnegie Mellon
• 9 Cisco 11 HP
• 2021 U. C. Davis 2789 Mauro (text author)
• 28471 Bremer AG (last one as of 4/14/07)

3
Configuring the Net-SNMP agent

• /etc/snmp/snmpd.conf
• Sets system group data
• Sets community names
• Sets trap destinations
• Configures internal extensions to monitor disk
  space, running processes, etc.
• Configures external extensions via exec commands

4

• If you put this in the snmp.conf file
• proc httpd 30 3
• proc sendmail 10 1
• proc snmptrapd 2 1
• You might get this when you walk the UCDavis
  private MIB procTable (2) subtree
• root_at_NetcommLinux rminch snmpwalk c ltcommgt
  localhost .1.3.6.1.4.1.2021.2
• enterprises.ucdavis.prTable.prEntry.prIndex.1 1
• enterprises.ucdavis.prTable.prEntry.prIndex.2 2
• enterprises.ucdavis.prTable.prEntry.prIndex.3 3
• enterprises.ucdavis.prTable.prEntry.prNames.1
  httpd
• enterprises.ucdavis.prTable.prEntry.prNames.2
  sendmail
• enterprises.ucdavis.prTable.prEntry.prNames.3
  snmptrapd
• enterprises.ucdavis.prTable.prEntry.prMin.1 3
• enterprises.ucdavis.prTable.prEntry.prMin.2 1
• enterprises.ucdavis.prTable.prEntry.prMin.3 1
• enterprises.ucdavis.prTable.prEntry.prMax.1 30

5

• If you put this in the snmp.conf file
• exec FileCheck /home/rminch/bin/checkfile.sh
  /home/devan/data/test.dat
• And checkfile.sh contains this
• root_at_NetcommLinux rminch cat
  /home/devan/bin/checkfile.sh
• !/bin/bash
• Checks for the existence of a file
• if -f 1 then
• exit 0
• fi
• exit 1
• And the file exists (you can verify thus)
• root_at_NetcommLinux rminch ls /home/devan/data
• authfail.dat test.dat userlimit.dat

6

• If you put this in the snmp.conf file
• disk / 10000
• And you check disk space via command
• rminch_at_ntcommlinux df -k /
• Filesystem 1K-blocks Used
  Available Use Mounted on
• /dev/sda2 16358040 9985740
  5541340 65 /
• You will get this when you walk the UCDavis
  private MIB diskTable (9) subtree
• rminch_at_ntcommlinux snmpwalk -c nt415r
  localhost .1.3.6.1.4.1.2021.9
• UCD-SNMP-MIBdskIndex.1 INTEGER 1
• UCD-SNMP-MIBdskPath.1 STRING /
• UCD-SNMP-MIBdskDevice.1 STRING /dev/sda2
• UCD-SNMP-MIBdskMinimum.1 INTEGER 10000
• UCD-SNMP-MIBdskMinPercent.1 INTEGER -1
• UCD-SNMP-MIBdskTotal.1 INTEGER 16358040

7
Extensible Agents

• Capabilities?
• Applications?
• Limitations?