Memory alerting issues in snmp monitoring

[mohan23]

Hi team,

I see physical memory of an Linux appliance that nagios is monitoring through snmp have issues, below are the issues:

1) Nagios is showing 86% physical memory usage of an appliance where as in appliance physical memory is shown as 16%. and below is the command we are running to get physical memory using snmp wizard in nagios

[nagios@lxappnagprd001 libexec]$ /usr/local/nagios/libexec/check_snmp_storage_wizard.pl -H 172.26.199.21 -C xcdgkpub --v2c -m Physical -w 75 -c 85 -f
Physical memory: 86%used(27653MB/32181MB) (>85%) : CRITICAL | 'Physical_memory'=27653MB;24136;27354;0;32181

when I run command to get memory usage instead of physical memory , I'm getting below output. and I see Physical memory and virtual memory usage as 86% (same usage) which I feel is something wrong and let me how the usage is being calculated and let me know how we can correct this.

[nagios@nagioshost libexec]$ /usr/local/nagios/libexec/check_snmp_storage_wizard.pl -H xxxxxxxx -C public --v2c -m memory -w 75 -c 85 -f
Shared memory: 100%used(977MB/977MB) Physical memory: 86%used(27652MB/32181MB) Cached memory: 100%used(23453MB/23453MB) Virtual memory: 86%used(27652MB/32181MB) (>85%) : CRITICAL | 'Shared_memory'=977MB;733;831;0;977 'Physical_memory'=27652MB;24136;27354;0;32181 'Cached_memory'=23453MB;17590;19935;0;23453 'Virtual_memory'=27652MB;24136;27354;0;32181

Can you some one let me know why virtual memory and physical memory are showing as same value. Ideally virtual and physical memory usage will be always different

[cdienger]

Use the "-v" option at the end of commands to show verbose output and identify where the values are coming from.

Some snmp checks for memory will not report data the way you'd like to see and you may need to use a different plugin. check_snmp_mem(https://support.nagios.com/forum/viewtopic.php?t=21832) for example may work better for you.

[mohan23]

Can you provide me link to download check_snmp_mem.pl ?

[mohan23]

check_snmp_mem script si alerting based on ram and swap.. but I need to alert on physical memory. can you let me know what is the script I can use to alert on physical memory ?

[cdienger]

Which command are you running on the remote machine to check the physical memory? I've tested with check_snmp_storage_wizard.pl and this seems to report the same physical total and used values for found with the 'top' command.

[mohan23]

Remote machine is a Debian pam appliance. When we compare to the output from Nagios to Pam appliance there is a huge difference. Nagios is showing 87% where as on appliance portal ram usage is showing as 13%.

As I have provided you the command line and output in my previous post, why virtual memory and physical memory are showing as 87% ?

[cdienger]

Because this is what the OIDs that are being polled are returning. The plugin does an snmpwalk over .1.3.6.1.2.1.25.2.3.1 to get the values used to calculate percentages and can be seen if you use the "-v" option. Physical memory can appear high because it can include cached/buffered memory that is actual treated more like free memory to the system. Virtual memory is a combination of swap and physical memory so the values being what they are could mean that there isn't any swap on the machine.