How to Troubleshoot Intermittent Network Problem
November 5, 2008 4:02 PM Subscribe
I have a new pc hooked up and it gets the Internet all the time, no problem checking e-mail, surfing or pinging anything on the WWW.
However, I have intermittent problems remotely logging into that machine, either via ssh or vnc. If I ping the machine for long intervals of time, I've seen packet loss of around 90%.
Does anybody have a good idea of where to start diagnosing this problem?
Response by poster: I'm using a wireless bridge connected to the PC's LAN.
The PC has zero issues with connecting to anything on the network or on the Internet.
The only problem is when I'm trying to log into the new machine from my older ones.
I use DD-WRT and have an IP address mapped to it's NIC MAC address.
I think what I'm gonna try to do first is hook up an ethernet cable from my laptop to the PC, then test the connectivity.
I fear that the culprit is my wireless bridge, but it could also be the PC's network card, perhaps its openssh-server?
posted by aereoperro at 4:21 PM on November 5, 2008
The PC has zero issues with connecting to anything on the network or on the Internet.
The only problem is when I'm trying to log into the new machine from my older ones.
I use DD-WRT and have an IP address mapped to it's NIC MAC address.
I think what I'm gonna try to do first is hook up an ethernet cable from my laptop to the PC, then test the connectivity.
I fear that the culprit is my wireless bridge, but it could also be the PC's network card, perhaps its openssh-server?
posted by aereoperro at 4:21 PM on November 5, 2008
Response by poster: Wireless Router DD-WRT
Wireless Bridge DD-WRT
New PC wired to Bridge
Wireless Laptop
posted by aereoperro at 6:00 PM on November 5, 2008
Wireless Bridge DD-WRT
New PC wired to Bridge
Wireless Laptop
posted by aereoperro at 6:00 PM on November 5, 2008
Best answer: One of the things about wireless is that its good for things like http (which is usually downloading a bunch of files) but is terrible when it needs to stream something like VNC, unless you have a good strong signal with very little noise and interference.
First thing I would do is ping my router from the wireless machine using different size packets. If you lose more than 1% packets then your wireless connection just isnt good enough for VNC. You can try repositioning the router so its closer to the computer or changing channels on the router. There are only three non-overlapping channels in wifi: 1, 6, and 11. So if youre on 6 then try 1 and 11.
If its intermittent then it may be that its fine until your neighbor fires up a torrent or starts microwaving his dinner.
I think what I'm gonna try to do first is hook up an Ethernet cable from my laptop to the PC, then test the connectivity.
Good idea.
posted by damn dirty ape at 6:06 PM on November 5, 2008
First thing I would do is ping my router from the wireless machine using different size packets. If you lose more than 1% packets then your wireless connection just isnt good enough for VNC. You can try repositioning the router so its closer to the computer or changing channels on the router. There are only three non-overlapping channels in wifi: 1, 6, and 11. So if youre on 6 then try 1 and 11.
If its intermittent then it may be that its fine until your neighbor fires up a torrent or starts microwaving his dinner.
I think what I'm gonna try to do first is hook up an Ethernet cable from my laptop to the PC, then test the connectivity.
Good idea.
posted by damn dirty ape at 6:06 PM on November 5, 2008
Whats the Signal to Noise on that bridge?
posted by damn dirty ape at 6:06 PM on November 5, 2008
posted by damn dirty ape at 6:06 PM on November 5, 2008
Response by poster: signal -53
noise -85
SNR 32
Signal Quality 50%
Hooked directly into my laptop's ethernet, I'm not dropping packets either way. So it is most likely the bridge's settings.
But it still strikes me as truly strange that the problem only pops up when I'm trying to log into the machine, or ping it. The Internet on the new machine never goes down, and it can always connect to other machines on my network.
posted by aereoperro at 6:27 PM on November 5, 2008
noise -85
SNR 32
Signal Quality 50%
Hooked directly into my laptop's ethernet, I'm not dropping packets either way. So it is most likely the bridge's settings.
But it still strikes me as truly strange that the problem only pops up when I'm trying to log into the machine, or ping it. The Internet on the new machine never goes down, and it can always connect to other machines on my network.
posted by aereoperro at 6:27 PM on November 5, 2008
SNR under 40, in my experience, can be troublesome. I'd try to reposition those devices or buy a nicer antenna for the bridge, perhaps directional. That is, if changing channels doesnt help. DD-WRT does a site-survey. You should see which channel is the least used.
Also, if youve played with the transmit level of the device, its worth noting that these little home routers have a crappy radio and the SNR suffers when boosted. Knock back down to stock levels or just a tad higher, under 40mw. You want the lowest amount of power it takes to get a clean SNR. I get a better SNR when the radio is set below the stock 24mw. Go figure.
You might also want to make the router/bridge G-Only and drop support for B.
posted by damn dirty ape at 6:44 PM on November 5, 2008
Also, if youve played with the transmit level of the device, its worth noting that these little home routers have a crappy radio and the SNR suffers when boosted. Knock back down to stock levels or just a tad higher, under 40mw. You want the lowest amount of power it takes to get a clean SNR. I get a better SNR when the radio is set below the stock 24mw. Go figure.
You might also want to make the router/bridge G-Only and drop support for B.
posted by damn dirty ape at 6:44 PM on November 5, 2008
Response by poster: Moving it three feet from its original position appears to have done the trick.
posted by aereoperro at 10:54 AM on November 7, 2008
posted by aereoperro at 10:54 AM on November 7, 2008
This thread is closed to new comments.
How are you connecting to it? From the internet or via your lan? Is the client computer on wireless? What is your internet connection like?
Do you get any packet loss pinging google.com from the computer?
posted by damn dirty ape at 4:06 PM on November 5, 2008