snmpwalk not working

[yngvi thorfinnsson_1]

Hi, I've two nodes on the same network,
but I'm not able to do snmpwalk.

snmpwalk -c public hermann.siminn.is system
snmpwalk: No response arrived before timeout.

on the host 'hermann.siminn.is':

snmpd -v

NET-SNMP version: 5.2.3



Can you help?

[Ivan Ferreira]

Try adding the -v option to indicate the version you want to use:

snmpwalk -Os -c public -v 1 hermann.siminn.is system

Ensure that no firewall is running or ensure that traffic is allowed.

[Mel Burslan]

telnet hermann.siminn.is 161

what do you see ?

[yngvi thorfinnsson_1]

rex# snmpwalk -c public -v 1 hermann.siminn.is system
snmpwalk: No response arrived before timeout.

rex# telnet hermann.siminn.is 161
Trying...
telnet: Unable to connect to remote host: Connection refused

[Mel Burslan]

connection refused for a targeted port telnet means, either a firewall between the source and target servers, not allowing traffic for port 161, snmp protocol or both depending on the behavior of the firewall, or, your snmpd is not running or not running on the default port 161.

On the target server, if you run these two commands:

ps -ef | grep -i snmp
netstat -an | grep 161

what output do you see ?

[Ivan Ferreira]

It seems that your service is not running at the server.

[yngvi thorfinnsson_1]

Thanks for the replies :-)


hermann:/# ps -ef | grep -i snmp
snmp 10415 1 0 15:03 ? 00:00:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1

hermann:/# netstat -an | grep 161
tcp6 0 0 :::8161 :::* LISTEN
tcp6 0 0 :::61613 :::* LISTEN
tcp6 0 0 :::61616 :::* LISTEN
tcp6 0 0 :::61617 :::* LISTEN
tcp6 0 0 ::ffff:157.157.19:36237 ::ffff:157.157.19:61616 TIME_WAIT
tcp6 0 0 ::ffff:157.157.19:36236 ::ffff:157.157.19:61616 TIME_WAIT
.
.
.

tcp6 0 0 ::ffff:157.157.19:36211 ::ffff:157.157.19:61616 TIME_WAIT
tcp6 0 0 ::ffff:157.157.19:36210 ::ffff:157.157.19:61616 TIME_WAIT
tcp6 0 0 ::ffff:127.0.0.1:61616 ::ffff:127.0.0.1:50104 ESTABLISHED
tcp6 0 0 ::ffff:157.157.19:61616 ::ffff:157.157.19:36244 ESTABLISHED
tcp6 0 0 ::ffff:127.0.0.1:50104 ::ffff:127.0.0.1:61616 ESTABLISHED
udp 0 0 127.0.0.1:161 0.0.0.0:*

[Mel Burslan]

Well, then your snmpd is running and listening on port 161 on the target server. Hence I have to say, the snmp traffic is not traversing from source to the target server, most probably due to a firewall or a filtering router of some sort in between the two.

[yngvi thorfinnsson_1]

we had to config this file as well

/etc/default/snmpd

as well as the

/etc/snmp/snmpd.conf

[Mel Burslan]

I am not very familiar with snmp on Linux platform but sounds like the snmp traffic is not reaching the target server at all. I'd suggest using something like tcpdump on the target server to verify this actually is the case. Then you can chase network team to figure out what is blacking the traffic and remove it.

Here is a page, showing you how you can run tcpdump for different scenarios.

http://linux.byexamples.com/archives/283/simple-usage-of-tcpdump/

Hope it helps