SNMP

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Simple Network Management Protocol

Online MIB Browser

http://www.oidview.com/mibs/0/HOST-RESOURCES-MIB.html - appears to have gone offline June 2020

https://bestmonitoringtools.com/mibdb/mibdb_search.php


Statistics

  • Source: Manager (Poller)
  • Destination: Device
  • Port: 161 UDP


Traps / Alarms

  • Source: Device
  • Destination: Manager
  • Port: 162 UDP


SNMP v3

Proviso

SNMP community string as used in the gui

&V3,[[Access Mode]]=Auth-MD5,[[Security Name]]=useridtext,[[Context Name]]=,[[Auth Passwd]]=authpwtext

SNMP Communtity string as used in the cli

snmpGet [[OID's]] sys Name.0 -S SNMPCOLLECTORNAME -P 3002 -r 3 -t 2 -c '&V3,[[AccessMode]]=Auth-MD5,[[Security Name]]=useridtext,[[Context Name]]=,[[Auth Passwd]]=authpwtext'


OIDs that use strings as the indexes

jnxSubscriberPortTerminatedCounter.3.112.115.51 = 14825

First int = length Proceeding ints, convert to hex, then hex to ascii in the example above

Length = 3
112 -> 70 -> p
115 -> 73 -> s
51 ->  33 --> 3
index = ps3

netsnmp will translate this when querying ie jnxSubscriberPortTerminatedCounter."ps3"

Net-SNMP

CLI command

./snmpget -v 3 -a MD5 -A 'authpwtext' -l authNoPriv -u useridtext 10.78.252.19 iso.3.6.1.2.1.1.5.0


Nice guide to comparing Juniper CLI to SNMP

qandaitem09186a00800b69ac.shtml www.cisco.com/en/US/tech/tk648/tk362/technologiesqandaitem09186a00800b69ac.shtml

Juniper CLI

show snmp mib walk ifDescr

Identify which net-snmp version is used in a particular Junos OS version

restart mib-process immediately
show log messages | match "NET-SNMP" | match mib2d 
May 25 07:38:15.434  jtac-lab-re0 mib2d[5920]: LIBJSNMP_NS_LOG_INFO: INFO: ns_subagent_open_session: NET-SNMP version 5.3.1 AgentX subagent Open-Sent!


Note: The command 'restart mib-process immediately' does not impact traffic. The process is respawned in seconds and during this brief time the network monitoring via SNMP is disrupted.

SNMP Version

  • RFC1213 - SNMPv1
  • RFC3416 - SNMPv2c
  • RFC3411-3415 - SNMPv3

Grafana

Because collectd doesnt us an inventory model - it doesnt appear to keep track or report on missed polls / values. We have to figure this out at the Grafana layer - looking for nulls. Except this isnt easy, we instead have to count how many values we have. This only works for the past 7 days / your raw retention period.

Find how many null values there are (thus missed pollings) - by counting how many values we have

  • Series - Choose a metric and using * for the hosts
  • Functions scale(0) offset(1) summarize(1h, sum, true)

95% billing

Will put a line at 95% usage on the graph. Target: scale(8)movingAverage(5min) 95%: nPercentile(#A,95)

Export and Import

When importing a dashboard - set id=null

SNMP Simulator

Used by librenms

http://snmplabs.com/snmpsim/index.html

snmpsim-command-responder = snmpsimd.py

data/variation files installed to

  • Ubuntu - /usr/local/snmpsim
python /usr/local/bin/snmpsimd.py --data-dir=/usr/local/snmpsim/data/ --variation-modules-dir=/usr/local/snmpsim/variation/ --agent-udpv4-endpoint=127.0.0.1:1024 
  • Centos - /usr/snmpsim
/usr/bin/snmpsimd.py --data-dir=/usr/snmpsim/data --variation-modules-dir=/usr/snmpsim/variation --agent-udpv4-endpoint=127.0.0.1:1024

Usage

https://www.ibm.com/support/pages/how-use-snmpsim-simulate-network-device-based-snmp-walk-file

Sample walks

https://github.com/etingof/snmpsim-data/tree/master/data/network/router


Linux force 64bit Counters

snmp.conf

## LibreNMS MIBs (restricted for faster polling)
## ---------------------------------------------------------
# Inc. System Info (name/loc) OIDs
view    libre-mibs      included        .1.3.6.1.2.1.1

# Include Interface MIBs
view    libre-mibs      included        .1.3.6.1.2.1.2

# Include Interface MIBs w/ 64 bit counters for high traffic boxes
view 	libre-mibs 	included	1.3.6.1.2.1.31

# Exclude 32 bit counters as high traffic boxes overflow
view	libre-mibs	excluded 	.1.3.6.1.2.1.2.2.1.10
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.11
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.12
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.13
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.14
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.15
view    libre-mibs.     excluded 	.1.3.6.1.2.1.2.2.1.16
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.17
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.18
view    libre-mibs      excluded        .1.3.6.1.2.1.2.2.1.19