How do I test the speed/reliability of a network?
April 10, 2013 1:39 PM   Subscribe

I have a somewhat complicated home network (see inside) that works OK most of the time but is occasionally unreliable. What software tools exist for testing the long-term reliability of a network (i.e. over several days)?

After asking this previous question, I set up my home network in the following way:

Cable Modem -> Main Router -> Powerline Adapter -> Secondary Router working as an Access Point

This gives me network access in the basement and another corner of the house (where the wireless from the main router wouldn't reach). This works OK much of the time, but I have annoying intermittent problems where I'll try to load a web page and it will just hang for, at times, close to a minute. Then everything will load and is fast again.

I can't tell if this problem is limited to wireless (it seems like it is, but 80-90% of our access is wireless) or if it's a problem with the PowerLine adapter (my current suspicion). I have moved the main router to the other side of the Powerline adapter and it seems better (suggesting it's NOT the Powerline), but problems often take a few days to crop up after I've reset my network hardware, so that's extra-annoying.

So, what I'd really like is tools with which I can test network connectivity or suggestions on how to troubleshoot. Since the problem is intermittent, any tools would need to be able to test the network over, at least, a 24 hour period. My technical skills are moderate and software that runs on a Mac is preferred (although I could dig out the Windows/Linux box if I really need to).

Ideas on what my problem might be are also welcome.
posted by Betelgeuse to Computers & Internet (6 answers total) 3 users marked this as a favorite
 
I'd probably take the approach of first trying to collect more information about whats going on, and when.

you could put something in your crontab to run every minute like "time wget http://ask.metafilter.com >> mefi.times" which will go out and get the webpage every minute and put the time output into mefi.times. Or no cron, just in a shell loop or something. Then maybe try the same thing at the same time for another totally different site. Do they hang at the same time?

you can also just get a terminal open and run ping forever to different hosts inside and outside your network. then let that scroll forever, and match the times with delays. Are you seeing packet loss from the pings?

Lastly, its hard to believe but swapping network cables is worth a try. I've recently gotten bit by bad cables (twice!) in the last month in an big enterprise data center - extremely tough to debug but the symptoms were kindof like how you describe.
posted by H. Roark at 2:52 PM on April 10, 2013


Ping plotter let's you ping or trace route multiple ips and graphs the results over time.
posted by empath at 3:07 PM on April 10, 2013


You need to figure out whether the problem is connection or DNS. That is when it 'hangs' is it hanging on looking up the hostname (which jives with the hanging for a minute or so while a lookup times out before going to the next server or retrying), or is it loosing all network connection.

Make a list of some common IP addresses that you can ping like: your ISP's gateway, your router's interface, somewhere out on the internet like Google's DNS (8.8.8.8) and the next time you have a hang see if you can ping the addresses directly. Also learn to check DNS resolution by tring to `ping example.com` vs `ping 192.0.43.10` or using the `host` or `dig` or `nslookup` commands (not sure what's the most common on OSX).

For just simple testing of connectivity I'd just start up a bunch of pings to IP addresses and log them to files for a few days and go back and look for lost packets or odd delays.
posted by zengargoyle at 3:19 PM on April 10, 2013


Do you have DHCP turned off for your secondary router?
posted by wongcorgi at 3:45 PM on April 10, 2013


Ping Plotter.
posted by Chocolate Pickle at 3:48 PM on April 10, 2013


The goal with troubleshooting is to eliminate things until you are left with the answer. So start with figuring out whether the issue happens on all clients, or just the ones connected to the secondary access point via the powerline adapter. If it's just the clients using the new AP and powerline adapter, start by running pings to the AP and see if it drops packets. If that's clean, move up to the router. Then the cable modem. One thing to try is to change the packet size to 1400 bytes or so. Sometimes glitches can be so intermittent that small 32 byte pings might not catch them. So use a full packet.

If that's all clear, then you can be fairly certain your local LAN is working fine, and have to start troubleshooting further. Using tracert to your ISP's website, start pinging the routers along the way. (Don't use the large packets here, it might make them angry.)

Or maybe it's something in a layer above the LAN. Maybe you have DHCP addresses timing out, or DNS problems. But best to start with the bits and wires first, especially if you just made changes.

Look in the mac's log files for errors that seem out of the ordinary.
posted by gjc at 3:51 PM on April 10, 2013


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