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We have a wireless access point at a client site. They say it goes down a lot. We replaced it. They say it still goes down a lot. Nobody's happy.

Now, in some instances, "WAP down" turned out to be a message from Outlook saying it lost connection to their hosted Exchange server. In one case, "WAP down" came from a desktop user on a wired connection... However, in other cases, it did seem like several people all lost their wireless connections at the same time. We know something's going on, we're just not sure what. (The firewall assures us that it is not losing WAN or LAN connections).

I have a little XP laptop that I'm going to drop at their site tomorrow and connect to the wireless network. I have some remote access / agent tools on it so I already have bit of a plan to try and watch availability.

However, I'm curious how other admins would approach this. Are there any great apps or tools that I might load on this laptop while it is on site? Tricks of the trade? Tips? I'm looking for more than ping -t google.com > pingtext.txt :-)

[added later]
The WAP is a SonicPoint N series, works in conjunction with the SonicWall NSA240 already there.

My diagnostic XP laptop will unfortunately be wifi only.

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4 Answers 4

up vote 4 down vote accepted

Ideally, I would setup something like smoke ping and monitor both the wired interface of the access point, and some device with a fixed IP that is always on.

Since you are dropping off that XP box, I would probably monitor the XP box, and the wired interface of the XP box from some other device on that network.

Monitoring from the XP box would tell you if the wireless link is lost, but it might not tell you if the AP software is confused, and just waiting for interference to go away might fix it.

Grabbing SNMP data, and enabling syslog are also good options to start.

If you do find that your wireless link is dropping, without a corresponding failure of the wired interface/snmp, then you may have some kind of interference. If it gets to this point, then it might then be time to break out the spectrum analyzer. Perhaps your outages are related to running that 30 year old microwave to heat their coffee.

If your link is dropping, you don't have a spectrum analyse, and your XP machine has a good wireless card,, I might consider firing up backtrack on it and running some of the wireless tools, to see what kind of interference you have from your neighbors.

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PingPlotter is another option. –  joeqwerty Jan 27 '12 at 1:30

This depends a lot on the AP. Many enterprise-grade APs (you're deploying these, right?) contain detailed logs and support shipping them to a syslog server, or support monitoring via SNMP.

It should be pretty easy to have detailed logs stored for later processing, but it depends entirely on your AP.

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If you're using a real WAP it should support SNMP. If you couple that with a monitoring system (e.g., Nagios, OpenNMS, etc.) you should be able to get detailed information about your WAP including things like client association/de-association, when a new DHCP lease is given out, and when it just fails completely.

If you're not using a real WAP (and you probably should) something like SmokePing will at least get you some connectivity information. Be warned though, just because your WAP responds to ICMP doesn't mean it's functioning correctly for clients. If your laptop is multi-homed you could just setup SmokePing on it. This is the cheap and easy answer... but really SNMP is probably the way to go here.

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SNMP is good, but a while ago, on an older access point, it returned snmp data that would indicate the network is working, when it wasn't. In this case where aren't sure where the problem is, it is best to collect as much data as you can easily get. So enable, and get snmp data if you are able, that is certainly good. But I still think having an active device on the wireless network that you can monitor is also pretty important. –  Zoredache Jan 27 '12 at 1:23

I have some experience with "enterprise grade" wifi periodically going down for no apparent reason.Things that helped were moving the access point around, for example, move from wall mounted to putting on top of the fridge or what have you. In addition the device itself can suffer from bitrot and it may help to add a little device which power cycles it periodically someetime in the night.

If the access point resides in a rather busy wifi neighbourhood it may become confused about that. It may help to limit the frequency bands it uses.

I found wifi analyzer on the android market to be helpful: https://market.android.com/details?id=com.farproc.wifi.analyzer&hl=en It can give you an idea about signal strength, how busy the airways are and a lot more.

I can only second the suggestion to use snmp.

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If you need to power-cycle an AP regularly, you don't have an enterprise grade AP or it's defective and should be replaced. Real enterprise gear does not need to be rebooted regularly like a $50 Linksys router. –  MDMarra Jan 27 '12 at 3:37
    
Right, that's why I used the phrase "enterprise grade", the quotes indicated sarcasm, which is a form of humour. –  aseq Jan 31 '12 at 1:57

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