Tag Archives: SNMP

Enabling SNMP on Xenserver 6

I spent an hour this afternoon cleaning up our OpManager install, making sure the new servers in the NZ office are monitored correctly.

And then I realised that we don’t have SNMP enabled on the XenServer hosts over there.

Turns out it’s not too hard though:

Edit /etc/sysconfig/iptables

Add in amongst the other allows:

-A RH-Firewall-1-INPUT -m state –state NEW -m udp -p udp –dport 161 -j ACCEPT

# service iptables restart

Edit /etc/snmp/snmpd.conf (aka change public to something more secure)

# service snmpd restart
# chkconfig snmpd on

Yup, that was easy 🙂

Enabling SNMP on Netgear DG834G

So we have a little Netgear DG834G in the development office. Yes it’s cheap, but it’s also quite rock solid, and we don’t really need anything more – so why spend the money on more?  The only thing is, I always tend to graph bandwidth usages on every router I have access to – helps troubleshoot latency issues etc..

The DG834G *supports* SNMP, however it has to be enabled manually whenever it’s rebooted.. Which thankfully isn’t very often for us!

I’ve configured my own (my second DSL modem!), back in the dark ages, but these days I run a Cisco 877 at home, so I had to do some google trawling..  And here’s how we do it 🙂

  1. Access your router on  (note: IP will likely be different – use your router’s IP)
  2. Enable SNMP and make your community name whatever you might wish. Click Apply.
  3. Type in the address bar: (it will say “Debug enabled”).
  4. Open a telnet session to the router’s IP (
  5. Type ‘iptables -D INPUT 1′ at the # prompt  – this removes the default block rule for SNMP.
  6. That’s it, your router will now respond to SNMP requests on port 161.

I’ve seen mention that folks need to re-delete the iptables rule, if they change their firewall rules, or if their modem reconnects to their ISP.. I haven’t experienced this myself – we change Optus account a couple of times a month (I’ll have to sort that out after christmas, it seems a little strange to have multiple accounts instead of just having a larger quota on one big account!), and when we rebooted the modem today, was the first time I’ve had to repeat this process.

Hope that helps someone out 🙂