>>> "Berger, Gary" <[EMAIL PROTECTED]> 08/11/06 12:58 PM >>> > I have used MRTG for network monitoring in one form or another for > about 12 years. Wow, you must have been among the first users...it only was made public in '96... ;)
Anyway, on to your questions... > Now, my question; we are monitoring our 25 locations from a > data center in Atlanta. Our latency to varies from between 30ms > to 55ms depending on the location. We currently have our polling > interval set to 5 minutes which I believe is the default. Yep, sure is...and the lowest resultion currently supported using MRTG as the poller. There are hacks to get this lower, but it is not recommended for the reasons below. > Of course this is controlled by Cron (we are running on Linux). Why "of course"? You can 'daemonize' mrtg and don't have to put it in cron. The downside is that each time you change the config, you'll need to restart the daemon. > Is it reasonable for me to think that I can set the polling > interval to 5 seconds and get a good response? No. Especially not with just using MRTG. If you switch to RRDTool for the backend, then set up your own poller (a number of pre-built ones are available like routers, mrtg-rrd, cacti and cricket to name a few), you'll get the information desired. But, in polling on a 5 second interval, you'll introduce a ton of interpolation because RRDTool will attempt to "normalize" the data obtained. On a 5 minute interval, a 1 second delay is not that big of a deal. On a 5 second interval, a 1 second delay would have a potentially astronomical effect on the data collected. That is not even taking into account the delay from the snmp process on the device giving you the requested information. > My experience in general has been that getting results > back from the SNMP queries of the routers takes longer > than this. Net/net I end up with missed samples etc. Yep, exactly. You may end up getting a whole lot of NaN results in your 5 second rra. > If this is not reasonable, can you recommend a tool > that can help me get this level of granularity on network > performance? My suspicion is that I will need to take a > distributed approach placing an MRTG box at every > location and have it watch the WAN port for that location. You'll still have the same problem. The devices won't be able to keep up with the requests. And since (hopefully) snmp is at the bottom of the priority queue, even below icmp, your snmp statistics will be totally unusable. > With this approach is it reasonable for me to expect a > polling interval of 5 seconds to be successful? No. You may be able to stick some device in between or on the same vlan that just collected the traffic and can respond, but that is doubtful as well. The only product I've seen that does a resonably close job of real-time monitoring are Visual Networks CSUs. Even then, you'll still end up with some missed polls, and those devices are in-line with the traffic, capturing everything that hits the WAN interface of the router, so you aren't adding anything at all to the router - it just costs lots of money. Paul -- Unsubscribe mailto:[EMAIL PROTECTED] Archive http://lists.ee.ethz.ch/mrtg FAQ http://faq.mrtg.org Homepage http://www.mrtg.org WebAdmin http://lists.ee.ethz.ch/lsg2.cgi
