Re: snmpd uses 100% cpu trying to enumerate IP Addresses

On Tue, 11 Mar 2014 11:05:09 +0000 Jenny wrote:
JL> snmpd uses 100% cpu most of the time trying to enumerate IPs (attaching
JL> with strace confirms that). It sleeps for few seconds, then comes back
JL> again to enumerate them, essentially using 100% CPU half of the time.
JL> Please note that we are not doing any snmp queries. Daemon is idle.
JL> 
JL> We need to measure NIC bandwidth and graphs. But we do not want the IPs
JL> enumerated.
JL> 
JL> How can we accomplish this? We can do compiling from sources (RHEL srpm).
JL> snmpd works beautifully in all our other machines.
JL> 
JL> net-snmp-5.5-49.el6.x86_64

Hi Jenny,

There is a pretty easy way around this, which is to exclude the
ipAddressTable. To do that, you'd modify your snmpd command to include

	-I -ipAddresssTable

Unfortunately, this causes a crash in another table. :-/

The way around that is to build without that table. In your spec file, look
for where MIBS is defined and delete ip-mib/ipv4InterfaceTable and
ip-mib/ipv6InterfaceTable.

When I rebuild like that, the -I option above eliminated the delay with
enumerating ipaddresses. You can verify this by running the agent like so:

  snmpd -f -Daccess:ipaddress:container -Lo -I -ipAddressTable udp:1161

without the -I option, you'll see tons of "access:ipaddress:container" debug messages. With it, you shouldn't see any. Tested on CentOS 6.5 with the srpm for the version you mention above.

Robert


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