Welcome to the great land of the snmp on cheap juniper network device. And be sorry. The paper of juniper is right.
Basicaly the snmp implementation of snmp in juniper is completly crappy as polling the device can completly kill the cpu, and so every userland daemons of the swith/routeur (rpd, lacpd, etc...) can suffer and have no time left to run, results in variety of bad things (lost of lacp link, routing protocol hang, etc...) Note: forwarding, routing is not affected.
This is completly stupid that snmp can kill vitals functions of a network device... but it was the case 
and juniper have no real plan to change this...
That says, this is not completly impossible to safely monitor this type of device using snmp (I suppose we talk about EX2200, 3300, 45XX, with cheap cpu, high end router do not pose problem).
You must avoid using snmpwalk on this device, specialy on IF part of the mib. That's why monitoring tools are not equal monitoring this type of devices :
- obversium is the worst, as it try to snmpwalk at each run almost the entire IF mib (and a lot of other). The result can be catastrophic.
Anyway the observium poller is just a joke.
- check mk (with basic interface) check do the same, but poll less part of the mib (but this can cause problem also). Afaik check_mk compile all snmp requests on one device and do walk on it.
- cacti is the right way to do : first poll to detect/scan wich interface are present (poller cache), and then at each run do small targetet snmpget.
So this is the way to do :
- implement a cache of oid to get (refresh it manualy)
- do targeted small snmp get, and better space it out.
I don't know if check_mk can be optimized (or de optimized) for handling such bad network devices.
Regards,
Le 10/11/15 21:46, Jam Mulch a �crit :
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I'm woefully ignorant about SNMP, but here's what I found from Google.
It seems Juniper wants their devices to be polled 'row by row' instead
of 'column by column' which
from what I've read, excludes using NetSNMP snmpwalk/bulkwalk.From:
Network Monitoring by using SNMP | Junos OS | Juniper Networks
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Raphael Mazelier
AS39605