lundi 25 février 2013

Check Point SPLAT SNMPv3 memory monitoring


Basic implementation of memory monitoring using snmp can lead to false alarm.
[Expert@FW1]# free
             total       used       free     shared    buffers     cached
Mem:       8308232    8027236     280996          0     249776    5983656
-/+ buffers/cache:    1793804    6514428
Swap:     18347752          0   18347752
In the example above, the firewall is running (208772 actives connexions)
The OS reports "8027236" of "8308232" used. However, we see that the
'free' + 'buffers' + 'cached' = "280996" + "249776" + "5983656" = "6514428", which is
'logically' free for applications to use, and will be handed out by the kernel appropriately.

According to sk32206: How to determine how much Free Memory is available on Linux/SecurePlatform systems
'Free Real Memory' should be equal to
- 'Free Real Memory' in output of 'cpstat -f memory os' command
- [ ('MemFree' + 'Buffers' + 'Cached') / 1024 ] from output of 'cat /proc/meminfo' command

Check out http://exchange.nagios.org/directory/Plugins/Network-Protocols/SNMP/Simple-snmp-memory-check/details
You'll find a very simple perl script to retrieve proper value of memory consumption.

[root@supervision plugins]# ./check_snmp_memory.pl -w 85 -c 95 -- -v3 -u USERNAME  -A '.xxx' -a MD5 -x DES -X 'xxxx' -l authPriv FW1
MEMORY OK: 21.57 % used; Free => 282472 Kb, Total => 8308232 Kb, Cached => 5983648 Kb, Buffered => 249772 Kb

We can compare with the result of cpstat on the firewall
[Expert@FW1]# cpstat -f memory os
Total Virtual Memory (Bytes):  27295727616
Active Virtual Memory (Bytes): 1836130304
Total Real Memory (Bytes):     8507629568
Active Real Memory (Bytes):    1836130304
Free Real Memory (Bytes):      6671499264
Memory Swaps/Sec:              -
Memory To Disk Transfers/Sec:  -

Let's do some math: 1 -(6671499264 / 8507629568) = 0.2158 => 21.58%  :-)

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