Dump SNMP information into file using Nagios - networking

Question

Is there any plugin of Nagios which can capture information from multiple SNMP agents and will dump snmpwalk information in a certain interval .
It will be better if information will be dumped in JSON format .

Answer 1

Because of the well documented plugin development guidelines, this is something you could easily build yourself!
Let's build one right now. Let's say we have 2 IP addresses, 192.168.1.10 and 192.168.1.11. We'll build a simple plugin using PHP, although you can ideally write it in any language you like.
This plugin isn't going to conform completely to the guides, but it should give you a nice starting point!
#!/usr/bin/php
<?php
// check if we have at least the minimum required output
// (we need at least 1 argument)
if (count($argv) < 2) {
echo <<<USAGE
Usage:
{$argv[0]} <outputfile> <address1>,<snmpcommunity1>,<snmpversion1>,<mib1> <address2>,<snmpcommunity2>,<snmpversion2>,<mib2> ...
USAGE;
exit(1);
}
// prep the data
$hosts = array();
$output = array();
$output_file = '';
for ($i = 1; $i < count($argv); $i++) {
$host = explode(",", $argv[$i]);
// we need exactly 4 elements
if (count($host) != 4) {
// unless of course we are specifying the output file to write the data to!
if (count($host) == 1) {
$output_file = $argv[$i];
continue;
}
echo "{$argv[$i]} IS INVALID. YOU MUST SPECIFY ALL OF: <address>,<snmpcommunity>,<snmpversion>,<mib>\n";
exit(1);
}
$hosts[] = array(
'address' => $host[0],
'snmp_community' => $host[1],
'snmp_version' => $host[2],
'mib' => $host[3],
);
}
// cycle through each host and gather the data
// this may take a while
foreach($hosts as $host) {
$snmpwalk_array = get_snmpwalk_lines($host['address'], $host['snmp_community'], $host['snmp_version'], $host['mib']);
$snmp_array = walk_lines_to_snmp_array($snmpwalk_array);
$output[$host['address']] = $snmp_array;
}
// convert the output array to json and put it in the file!
$json = json_encode($output);
file_put_contents($output_file, $json);
$num_hosts = count($hosts);
echo "OK - {$num_hosts} PROCESSED\n";
exit(0);
// format an array in a sane way from snmp walk output
// this will return an array like:
// [oid][type] = 'Counter32'
// [oid][value] = 0011232
// etc.
function walk_lines_to_snmp_array($walk_arr) {
$snmp = array();
foreach ($walk_arr as $line) {
$oid = convert_snmpwalk_line_to_array($line, $arr);
if ($oid !== false)
$snmp[$oid] = $arr;
}
return $snmp;
}
// return an array of an executed snmpwalk output
function get_snmpwalk_lines($address, $snmp_community, $snmp_version, $mib) {
$cmd = "snmpwalk -c {$snmp_community} -v {$snmp_version} {$address} -m {$mib}";
exec($cmd, $output);
return $output;
}
// return the oid and pass the array by ref
// or return false on failure
function convert_snmpwalk_line_to_array($line, &$arr) {
if (preg_match('/(.*) = (.*): (.*)/', $line, $matches) === 1) {
$arr = array(
'type' => $matches[2],
'value' => $matches[3],
);
return $matches[1];
}
return false;
}
Now, you can put this in a file in your $USER1$ directory (/usr/local/nagios/libexec) named check_multi_snmpwalk.php and make sure it's executable chmod +x /usr/local/nagios/libexec/check_multi_snmpwalk.php.
Finally, all we need to do is define a command for Nagios to pick it up and use it! Something like the following should suffice:
define command {
command_name check_multi_snmpwalk
command_line $USER1$/check_multi_snmpwalk.php $ARG1$ $ARG2$ $ARG3$ $ARG4$
}
Now you should be able to specify the file you want the JSON to be output to in ARG1, and then each other argument needs to contain the host address, the snmp community, the snmp version and the mib you want to walk.
So, for example:
define service {
host_name localhost
service_description Multi SNMP Walk
use local-service
check_command check_multi_snmpwalk!/tmp/jsonfile!192.168.1.10,community,1,all!192.168.1.11,community,2c,all!!
register 1
}
Now you're saying "Okay, thats all great, but what does it do?!"
I'm glad you asked! This is what it does:
Grabbing some input from the user (what are we snmp walking?)
Executing an snmpwalk (and saving the output) for each host specified
Converting the snmpwalk output to an easy-to-read array
Aggregating each host's snmpwalk easy-to-read array into a giant array
Converting the giant array to JSON
Writing the JSON to the file specified
Returning an OK Status for Nagios with a message stating how many hosts we processed!
A few notes:
This plugin will take a while to run no matter how many hosts you specify, so you may want to consider running it from a cron job instead of a Nagios check
This plugin does NOT conform to the plugin guidelines I linked to earlier, but it was still a fun little project
Hope this helped!