Christopher McAtackney wrote: > 2009/3/25 Kevin Keane <subscript...@kkeane.com>: > >> I think you are comparing apples and oranges here, because in most >> situations that I can think of, the decision is dictated by the network >> topology. If you are exclusively on a trusted private network, >> check_by_ssh really doesn't offer any benefits. Conversely, if your >> topology involves the Internet or some other untrusted network (WiFi), >> then you wouldn't want NRPE in the first place. >> >> The only exception to the above that I can think of is when it comes to >> deciding between using check_by_ssh over an untrusted network, vs. NRPE >> through some other kind of tunnel or VPN. But in that case, you'd incur >> encryption overhead either way, and the comparison is very different >> from the question you asked. >> >> All that said: I don't have any first-hand experience, but I suspect >> that the impact of establishing 2200 ssh connections in a five-minute >> span (assuming that you are using a five-minute check interval) is >> pretty substantial. The main impact actually lies in establishing and >> tearing down the connections, key negotiations etc.; the encryption >> during the data phase probably has only limited impact because most >> checks only transmit a few bytes back and forth. >> >> SSH does much better with longer-duration connections when the keys are >> already exchanged. This is even more true if you have a router-based >> VPN, because in that case the overhead is offloaded to a different machine. >> >> So if you have the option of sending the checks as NRPE through one or a >> few long-term VPNs: you are probably going to be better off. Of course, >> in the big picture, your mileage may vary. >> > > Firstly, thanks for the detailed explanation of the issues involved in > this choice Kevin, it's been very helpful. > > I'm curious though, could you elaborate on why NRPE is unsuitable if > communication with my remote hosts is going to go via the Internet? Is > it not sufficient that NRPE uses SSL? This may be more of a network > security question than a Nagios one, but I've no real experience in > either area unfortunately, so I appreciate any info you can give here. > No, you are right. I wasn't aware that NRPE could use SSL. In that case, NRPE would be pretty much the same in terms of performance as SSL.
That said, I am generally concerned from a security standpoint about any kind of active checks going over the Internet. This is because if you are monitoring, in your example, 200 hosts, you have to poke holes into 200 firewalls (or into one firewall, and then set up SSL or SSH keys on 200 hosts). That's 200 potential security holes all over the place with little or no control, and on machines that may not necessarily be hardened for access from the outside world. Worse - active checks, by nature, cause a program to be launched and executed on the monitored client, and usually with very high permissions. You said that you check 2000 services, so that's 2000 plugins (give or take a few). What if a hacker found a way to compromise one of your 2000 plugins? You'd have a privilege escalation issue along with remote-launch capability. On 200 clients. Because of these concerns, I am using passive checks almost exclusively over the Internet (except for publicly available services such as HTTP or SMTP, of course); I wrote an agent that resides on the client as a wrapper around the excellent NSClient++ and performs the actual checks. It then forwards the checks to the Nagios server via NSCA over HTTPS. A second benefit is that this agent collects about 40 or so check results, and then sends all of them at once through a single SSL connection. That reduces the overhead of establishing a secure connection by a factor of 40. BTW, the agent is available as Open Source. Go to http://www.tntmonitoring.com . -- Kevin Keane Owner The NetTech Find the Uncommon: Expert Solutions for a Network You Never Have to Think About Office: 866-642-7116 http://www.4nettech.com This e-mail and attachments, if any, may contain confidential and/or proprietary information. Please be advised that the unauthorized use or disclosure of the information is strictly prohibited. The information herein is intended only for use by the intended recipient(s) named above. If you have received this transmission in error, please notify the sender immediately and permanently delete the e-mail and any copies, printouts or attachments thereof. ------------------------------------------------------------------------------ _______________________________________________ Nagios-users mailing list Nagios-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nagios-users ::: Please include Nagios version, plugin version (-v) and OS when reporting any issue. ::: Messages without supporting info will risk being sent to /dev/null
