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SNMP Trap Integration

SNMP trap listener sends alerts to Alerta.

For help, join Slack chat

Prerequisites

  • Net-SNMP snmptrapd package - integration runs as a trap handler by Net-SNMP snmptrapd

To install net-snmp on RedHat/Centos Linux:

$ sudo yum -y install net-snmp net-snmp-utils

To install net-snmp on Ubuntu Xenial:

$ sudo apt install -y snmptrapd snmp

Installation

Clone the GitHub repo and run:

$ python setup.py install

Or, to install remotely from GitHub run:

$ pip install git+https://github.com/alerta/alerta-contrib.git#subdirectory=integrations/snmptrap

Configuration

Configure snmptrapd to execute alerta-snmptrap when an SNMP trap is received:

$ vi /etc/snmp/snmptrapd.conf

authCommunity log,execute,net public
format execute $a %a\n$A %A\n$s %s\n$b %b\n$B %B\n$x %#y-%#02m-%#02l\n$X %#02.2h:%#02.2j:%#02.2k\n$N %N\n$q %q\n$P %P\n$t %t\n$T %T\n$w %w\n$W %W\n%V~\%~%v\n
traphandle default /path/to/alerta-snmptrap

NOTE: Use the full path to the alerta-snmptrap script because snmpstrapd only searches a few paths. Use which alerta-snmptrap to get the full path for your installation.

Set Alerta API endpoint and load all MIBs in the start-up script on RedHat/Centos:

$ vi /etc/sysconfig/snmptrapd

export MIBS=+ALL
TRAPDRUN=yes
export ALERTA_ENDPOINT="http://localhost:8080"

Set Alerta API endpoint and load all MIBs in the start-up script on Debian/Ubuntu:

$ vi /etc/default/snmptrapd

export MIBS=+ALL
TRAPDRUN=yes
export ALERTA_ENDPOINT="http://localhost:8080"

Restart the snmptrapd service:

$ sudo service snmptrapd restart

SNMP MIBs

Download all base SNMP MIBs and any MIBs required for the specific environment eg. Cisco, NetApp, Dell.

On Ubuntu, use snmp-mibs-downloader to download MIBs and install them in the correct directory:

$ apt-get install snmp-mibs-downloader

To test that the downloaded SNMP MIBs are used to translate any received traps translate a "coldStart" trap with and without the "-m +ALL" option, like so:

$ snmptranslate .1.3.6.1.6.3.1.1.5.1
iso.3.6.1.6.3.1.1.5.1

$ snmptranslate -m +ALL .1.3.6.1.6.3.1.1.5.1
SNMPv2-MIB::coldStart

Transform Plugin

By default, SNMP traps are assigned reasonable values for each alert attribute. However, to make SNMP traps useful sources of events it may be necessary to do additional processing and assign relevant values for resource, event, severity and others.

To achieve this in an extensible way, it is recommended to use a plugin that transforms the original "trapvar" values stored as attributes in the submitted SNMP trap alert to values like severity in the "pre-receive" hook.

Example Trapvars

  "alert": {
    "attributes": {
      "trapvars": {
        "_#": "3",
        "_1": "0:1:41:43.19",
        "_2": "iso.3.6.1.6.3.1.1.5.3.0",
        "_3": "\"This is a test linkDown trap\"",
        "_A": "0.0.0.0",
        "_B": "localhost",
        "_N": ".",
        "_O": "iso.3.6.1.6.3.1.1.5.3.0",
        "_P": "TRAP2, SNMP v2c, community public",
        "_T": "0",
        "_W": "Enterprise Specific",
        "_X": "15:05:45",
        "_a": "0.0.0.0",
        "_b": "UDP: [127.0.0.1]:48476->[127.0.0.1]:162",
        "_q": "0",
        "_s": "SNMPv2c",
        "_t": "1482073545",
        "_w": "6",
        "_x": "2016-12-18"
      }
    },
    ...

Example Transform Plugin for Oracle EM Traps

class OracleTrapTransformer(PluginBase):

    def pre_receive(self, alert):

        alert.resource = alert.attributes['trapvars']['_3'].split('.',1)[0]

        if alert.attributes['trapvars']['_10'] in ['Serious', 'Critical']: # oraEM4AlertSeverity
            alert.severity = 'critical'
        elif alert.attributes['trapvars']['_10'] == 'Error'
            alert.severity = 'major'
        else:
            alert.severity = 'normal'

        alert.event = alert.attributes['trapvars']['_6'].replace(' ','')   # oraEM4AlertMetricName
        alert.value = alert.attributes['trapvars']['_14']                  # oraEM4AlertMetricValue
        alert.text = alert.attributes['trapvars']['_11']                   # oraEM4AlertMessage

        return alert

    def post_receive(self, alert):
        ...

Snmptrap Format

trapvar Description
$a the contents of the agent-addr field of the PDU (v1 TRAPs only)
$A the hostname corresponding to the contents of the agent-addr field of the PDU, if available,
otherwise the contents of the agent-addr field of the PDU (v1 TRAPs only).
$b PDU source address (Note: this is not necessarily an IPv4 address)
$B PDU source hostname if available, otherwise PDU source address (see note above)
$N enterprise string
$O oid as name or numbers
$P security information from the PDU (community name for v1/v2c, user and context for v3)
$q trap sub-type (numeric, in decimal)
$s SNMP Version
$t decimal number of seconds since the operating system epoch (as returned by time(2))
$T the value of the sysUpTime.0 varbind in seconds
$w trap number
$W trap description
$x current date
$X current time
$<n> nth attribute
$# number of varbinds

See http://net-snmp.sourceforge.net/docs/man/snmptrapd.html

Troubleshooting

Stop snmptrapd and run it in the foreground:

$ sudo service snmptrapd stop
$ sudo ALERTA_ENDPOINT="http://localhost:8080" snmptrapd -m +ALL -Lsd -p /var/run/snmptrapd.pid -f

Tail syslog file:

$ tail -f /var/log/messages

Send test traps:

$ sudo snmptrap -v2c -c public localhost "" .1.3.6.1.6.3.1.1.5.3.0 0 s "This is a test linkDown trap"
$ sudo snmptrap -v2c -c public localhost "" .1.3.6.1.6.3.1.1.5.4.0 0 s "This is a test linkUp trap"

If the trap is not processed and nothing appears in the logs use strace to generate system-level tracing of the daemon:

$ ps -ef | grep snmp
$ strace -ff -p <pid>

Example strace Output

[pid 23125] rt_sigaction(SIGTERM, NULL, {SIG_DFL, [], 0}, 8) = 0
[pid 23125] rt_sigaction(SIGTERM, {SIG_DFL, ~[RTMIN RT_1], SA_RESTORER, 0x7f3dc8225cb0}, NULL, 8) = 0
[pid 23125] stat("/sbin/alerta-snmptrap", 0x7fffc9511a70) = -1 ENOENT (No such file or directory)
[pid 23125] stat("/usr/sbin/alerta-snmptrap", 0x7fffc9511a70) = -1 ENOENT (No such file or directory)
[pid 23125] stat("/bin/alerta-snmptrap", 0x7fffc9511a70) = -1 ENOENT (No such file or directory)
[pid 23125] stat("/usr/bin/alerta-snmptrap", 0x7fffc9511a70) = -1 ENOENT (No such file or directory)
[pid 23125] write(2, "sh: 1: ", 7)      = 7
[pid 23125] write(2, "alerta-snmptrap: not found", 26) = 26
[pid 23125] write(2, "\n", 1)           = 1
[pid 23125] exit_group(127)             = ?
[pid 23125] +++ exited with 127 +++

From the above error it can be seen that is this example the alerta-snmptrap script can't be found by snmptrapd which is why the trap isn't being processed.

References

License

Copyright (c) 2014-2017 Nick Satterly. Available under the MIT License.