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ZT, http://www.linuxquestions.org/questions/linux-networking-3/w

(2012-02-26 20:42:37) 下一个

I've used both DD-WRT as well was OpenWRT on a few different devices. They both work very well, and would choose OpenWRT over DD-WRT mainly because I don't need a GUI (or want) to configure the device. Once one gets used to the syntax involved with the files found in /etc/config, it's pretty simple. Well, if you have a basic understanding of TCP/IP, firewalls and routers, that is.

I noticed something running on port 80 of an access point I installed OpenWRT on today. I didn't bother checking it out, and it will be disabled as soon as I install it as the main AP here at home.

I received a Ubiquiti NanoStation2 today that appears it will do well. Using the instructions found here, I had OpenWRT (Backfire 10.03 Beta) installed on it within minutes. I was only using the GUI to update the firmware that came with the device, which I did not bother to check out beyond finding the firmware update page.

I then proceeded to lock myself out of the device as I forgot to add access for ssh after I reconfigured the network. tftp'ed the image to it at that point and everything was good. There is only one ethernet port on this device, and it's firewalled by the default config. As I recall, the first time the device boots on a OpenWRT install, it disables the firewall and enables telnet. Telnet is disabled after you change your password, but I'm not sure if that is what also enables the firewall, or if that's merely the result of the firstboot script. Either way, keep that in mind if you do decide to use OpenWRT.

The NanoStation2 strikes me as an excellent value. In some testing I've done with it thus far, the throughput is extremely high. I did some file transfers on it and found the throughput to be just a wee bit over 23Mb/sec, which is pretty impressive. That was with a damn near line of sight connection, however, and only 15 feet away, which is closer than it will be when installed, not to mention the signal will then be going through a floor at least. Here is a portion of an article I found on the Tech World site:



Quote:







The fact is that real Wi-Fi speeds, measured in terms of file transfers, have always been slower than the claimed data rate. This is because headers, handshakes and other overhead take up a substantial amount of the available bandwidth. Here are the real file transfer speeds I measured with each class of WLAN product:

* 802.11b, nominally 11 Mbit/s, actual throughput 4.5Mbit/s
* 802.11g, nominally 54 Mbit/s, actual throughput 18 Mbit/s
* Boosted G, nominally 108 Mbit/s or 125 Mbit/s, actual throughput 22 to 24 Mbit/s


I downloaded a ~600 meg file, and was getting 23.2Mb/sec throughput. The client system was using a Linksys WUSB54GC adapter, which has no external antenna at all.

Still, when doing scans from another system that has a 5dBi antenna on it, I was still getting a 100% signal going through two fairly thick walls at somewhere around 10 meters away.

I also have OpenWRT (Kamikaze 8.09) installed on a Belkin F5D8230-4 wireless router that works well, but nothing like that NanoStation2. That particular router is a pre-N device, although I pulled the miniPCI card as OpenWRT did not have a driver for it, and I didn't feel like screwing around with the one available for it, either. I installed a Broadcom 4312 card, which seemed to work well enough. Last week I had a 9dBi rubber duck antenna lying around with no particular use, so I took two Ufl to RP-TNC adapters I had, drilled two holes in the top of the router and ordered another antenna. It came in yesterday, and I'm not particularly impressed with the performance of the device, although it's definitely better than it was. The NanoStation2 has considerably higher output, which is one of the reasons, as it has dual 10dBi antennas built into it. When the Belkin router was placed where I was getting a 100% signal from the NanoStation, it was at 70%-75%. Actually, that isn't bad at all I suppose.

I'll probably buy a higher output Atheros or Broadcom card for it and see how it performs then. Seeing the cost of the antennas and adapters for that router ran somewhere around $60, it's not the most cost effective way of going about things. A good high power card will be another $60.

I also have a Buffalo WLI2-TX1-G54 wireless bridge running DD-WRT. It performs incredibly well considering it does not even have an external antenna on it at all. I would have put OpenWRT on it, but it simply would not function correctly. I attempted to get it to work for quite a while, actually. I'll be pulling it when I install the NanoStation2, so I'll slap a serial port on it, and check out what OpenWRT is doing once I get a chance. With DD-WRT, at somewhere around 15 meters where the signal is going through a floor and probably a wall at ~30 deg angle, I pull 75%-80% signal strength.

I seem to recall DD-WRT is more restrictive with regard to configuration options than OpenWRT. When I started wandering off the beaten track, it wouldn't cooperate. I remember it was using NVRAM for configuration, whereas OpenWRT does not use it now, or at least not since Kamikaze as I am aware for a main configuration utility. It is utilizing UCI (Unified Configuration Interface) which is far better as far as I am concerned. I don't think the configuration interfaces themselves are the reason for DD-WRT being more restrictive, however.

I imagine that OpenWRT would perform well enough on the Linksys WRT54G router you have - maybe. Look at the OpenWRT WIKI page for WRT54G routers to determine if yours is one that is supported. Take note of this:

WRT54G v5, v5.1, v6, v7 and v8

This version has switched to a proprietary non-Linux OS (WikiPedia:VxWorks). It has less flash (2 MB) and less RAM (8 MB). These versions are NOT supported.

My Belkin F5D8230-4 has a 264MHz processor with 4 meg of flash, 16 meg of RAM, whereas my Buffalo WLI2-TX1-G54 has 125MHz/4M/16M. Try to find a router with 4M of flash (or more) -- 2M is possible, but leaves you with no options to install anything other than a very basic router package. You'll likely not have any useful tools like tcpdump available then as there is no space for them.

I wouldn't recommend a Belkin like the one I have for a first project. It wasn't easy to get OpenWRT installed and running on that thing. I do have to give it some credit from a hardware standpoint, however. It's the best built home router I've ever taken apart. The PCB has metal shielding that encases the whole thing, with easily removed covers. The miniPCI card that came with it was one of the massive ones, so I'm not limited to the typical cards that only fit in laptops. I should be able to use it for several more years if I'm so inclined -- if new wireless cards are released as miniPCI.

Oh -- something I thought I'd mention: for some odd reason my HTC Magic running Android does not work with the NanoStation2. I was able to connect wirelessly to the device with both Linux and OpenBSD systems, but that damn phone starts arping for itself once it gets a DHCP lease. There is a burst of throughput at connection, then arp requests. The only difference I can see right off hand between the NanoStation2 and my other wireless devices is that it uses an Atheros chipset as opposed to Broadcom on everything else I have. Could be the beta release of OpenWRT, but I've read this has happened to a number of people going back to the G1 handset.

Good luck with your project. I enjoy working on wireless devices, and particularly enjoy the ones that present a challenge. That NanoStation2 was actually too easy.


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