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Hardware

Wireless Networking w/o An Access Point? 18

Posted by Cliff from the can-it-be-done? dept.
vluther asks: "I was curious if anyone here had used any wireless networking solutions for their house/SOHO. I'm a perl hacker, not a networking guru, I can do basic stuff, but I am nowhere near a network admin. I have tried to describe my setup below, hopefully it will help. I've been looking at the WebGear Aviator 2.4, and the Symphony from Proxim, but both of them come with an option of buying an "access point", which claims to allow for "seamless integration" with your existing wired network. Yet the average home networking kit these guys sell doesn't come with the "Access Point", the thing even costs $399 for Proxim's, and $599 for WebGears. My question is, will I need to purchase one of these if I have my existing setup or can I just buy the Networking kit from Compusa, and get my Internet access/filesharing going?"

"I can't get a wired network because I rent the place, besides running wires from basement to second floor is ugly. My setup is as follows:

  1. 1 Desktop connected to net via SDSL, Running Windows 98 SE, (in basement)
  2. 1 Desktop running Linux connected to net via SDSL (I have two static IPs).
  3. 1 IBM Thinkpad, + 1 IBM Aptiva looking to get on the net via the SDSL, but they are two floors up
What all would I have to do/know before I can share my mp3s in my room on the second floor? :). Adding additional internal ips (192.168.blah?) to the pc's already connected to the net? If so.. does 98 allow more than 1 nic? Will I need to change broadcast addresses/netmasks? Will be very greatful for your opinion. "
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Wireless Networking w/o An Access Point? More

Wireless Networking w/o An Access Point?

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  • What you are looking for is ipalias, it is an option in the Linux kernel. It allows you to create virtual network devices on top of physical ones. If you have eth0 as a physical NIC and an IP address, you can then create eth0:n with ipalias, such that for each value of 'n', it is a different virtual network card with a different ip address. So eth0 can be 192.168.4.1 on the 192.168.4.0/24 network, and eth0:1 can be 192.168.5.1 on the 192.168.5.0/24 network, but both are the same physical card connected to the same physical medium. Look at network howtos and kernels docs for more information.

    Now, you can simple setup two networks (one for each end of the room) and have the middle computer route between the two subnets. Or you can use brigding if you want only a single subnet, but the linux bridging code is still experimental. Hope this helps.
    ------------------------------------------ ----------------------------------

  • 1/4 mile, huh? What's to stop a neighbor from plugging in his own wireless card and piggybacking off of you? Or the "black helicopters" from tapping your signal and looking at all of your porn or listening to your MP3's?

    While asked in a jesting manner, privacy issues like these are the only thing stopping me from getting some of the new 11mb wireless gear for home and work (now that I have a laptop that lets me work for more than and hour on battery, yay!).
  • Well, the obvious thing _can_ happen, but only if you tell it to.

    If the machine at C is capable of IP routing, and you enable it, and it's capable of having more than one IP address on an interface, and you give the RF interface two addresses, and A and B are on _different_ subnets, then yes, you can get there from here.

    Theoretically. I'm not 100.0% positive that the 802.11 cards will handle being checked into a network with more than one IP address correctly.

    It might be easier to solve this problem at the RF level: use gain antennas. At those frequencies, they won't have to be very big...

    Cheers,
    -- jra
    -----
  • But maybe somebody will see this anyway.
    I was wondering about the possiblities of a jury-rigged wireless network with "rubber-duckie" antennae with BNC connnectors attached to NIC cards. The cards are essentially transceivers, if the antenna gives it the proper impedance to work into, could this work over short distances, like inside a house?
  • One should choose a landlord as carefully as one wishes one had chosen a spouse.
  • If I buy three wireless LAN equiped laptops (such as those ibooks or PCs with cards, whatever) and arrange them so that laptop A is at one end of a very long room, and laptop B is at the other end of the room, so that B and A *cannot* communicate, but I place C in the middle such that B and C *can* talk and A and C *can* talk -- does the obvious thing happen ?

    Easy answer: Nope, not usually. Wouldn't it be nice? :)

    Hard answer: You can do this yourself, as I see another poster as already described. But, that method may or may not work depending on your network interfaces.

    For example: I use a lot of Aironet cards at work, since we do some wireless interfacing between all sorts of various devices. One thing we do is switch the card, programatically (sp?), between using the access point, and using ad-hoc (really peer-to-peer, IMHO, but let them call it what they will).

    In peer-to-peer mode, it just broadcasts the packet out with a destination address. Anyone else in peer-to-peer just looks at everything coming in to see if it's for them. If it's not, they ignore it.

    In other words, if A is sending to B, and C sees the packet going to B, it ignores it in the driver and the packet never reaches the upper layer (my software). Since it never gets to B at all because of distance, B doesn't get squat.

    There are workarounds. You can stick C into promicuious (sp?) mode, where it watches everything. I've used that as a sniffer to see what's going on for debugging sometimes (The aironet guys we talked to about it were amazed when we showed them how we could watch the packets flying across the airwaves like that and said they'd never thought of using it that way before)..

    The access points WILL do what you're thinking, but not when the devices are in ad-hoc mode. Access points ignore ad-hoc communication. The access point method involves a device registering with the access point and then routing ALL communication through it. If two devices are registered to the same access point, the communication doesn't go through a wire, but still gets routed through the acces point. With multiple access points, the devices switch around between them rather quickly and flagrantly, if you have overlapping coverage. In this mode, no two wireless devices ever talk directly, they always go through the access points (which communicate to each other over the wire networks, if needed).

    This ZoomAir software sounds like it does the same thing as an access point. I have done something like this with an access point before. It doesn't have to be connected to the wire to pass messages in it's own coverage area, so the software probably can do the same.

    ---
  • It's not as jesting as you think.

    Some of the manufacturing plants I've installed stuff like this at have huge, overlapping coverage, because of so much machine noise in the plant itself. Since I always take the laptop + radio card with me, I've tested a few of them. It's AMAZING the kind of distance you can get from some of these places. At one plant (I won't say which), it's almost trivial to get on their network from about 1/8 mile away, outside the plant. Not to say that it doesn't come in handy when I'm staying at the hotel next door, but security? Forget it.

    ---
  • Depending on the DSL router you may not even need the linux box to do the IP Masq.

    Many of the DSL routers (The Cisco ones for sure,) will do that for you.

    I've been setting up a lot of offices with the Cisco routers and all I have to do is plug it into the hub and point all the workstation's gateways to it. Simple.
  • Wireless is deffinatly a great solution for your situation.
    I've been using Aironet 4500 (2 mb) at my office for about a year.

    I have two base stations. One is in the warehouse and is hooked up to a 12db omni mast on the roof (gives me about 1/4 mile range) and a 8db omni inside. It is connected to the ethernet hub which is connected to an ISDN.

    The other base station is unwired and is used as a reapeater/bridge from the office to the warehouse.

    Base stations are just computers running routing and brigding software. The Aironet routers are Motorola PPCs with an internal PCMCIA and retail wireless NIC (it even has the stickers on it).

    The base stations just make installation and integration with a wired LAN easy.

    If you are comfortable with getting a wireless NIC working under linux, then save some money and skip the base station.

    All you would need is to get routed working on the linux box. If it is a good router (like a Cisco) it can do the IP Masq. for you. If it also has DHCP don't even worry about the 192.168.blah, just point the gateway on all the machines to the router and let it do the work

    I personaly would avoid integating the wireless thru the windows machine. Its just a little too unstable.
  • Hey, I never said my method was easy - but it would have to be cheaper, and maybe more reliable (unless you tend to move that laptop around a lot, flopping on the couch to do some coding or whatever - personally, I have never done this, and don't think it would be comfortable, but I can understand the appeal).

    If one is dealing with a person, on a normal house or such (the vision I was having was that the building was a brownstone or one of those SF style Victorians - tall and narrow), then it would be a good idea to approach the person. However, if that doesn't work, I say screw 'em, and do it quietly.

    It can be possible to do the work quietly (though it will be MUCH slower, and maybe impossible if one has to go through concrete). Unless the landlord lives on-site (as in the same building, where noise will be the issue), there shouldn't be any problem doing surreptitious mods (provided they are discrete, and are made to look good).

    The way the person was describing the building, though, was that he lived on all three floors - one wouldn't have to run the wire in the walls - run it between the floors, by drilling up through the ceiling/down through the floor (peel back the carpet first). When you move out, cut and remove the cable, and patch the holes. Done right, with an artistic touch, you will not be able to tell.

    As far as building codes? I wouldn't worry about them unless you running near electrical outlets (though I did suggest this), or you are running electrical cable. An ethernet cable is not going to impact anything. I agree with your suggestion of conduit, and of mentioning the improvements as a plus to the landlord. But you have to know your landlord - how nice are they, etc - before mentioning if. If the landlord is an ass - don't mention it, get denied, then do it - suspicion is on you, then.

    Finally, all bets are off if your landlord likes to take regular "tours" of your place while you are away. If this is the case, I think you may have bigger problems, and may want to look into a video security system while you're at it...
  • I don't know whether or not you simply want two SDSL connections, but you don't really need them both. All you have to do is set up Linux using IP Masquerading and give all the other machines 192.168.* addresses. You'll save the monthly fees for the connection and the static IP.

    As for the wireless lan, I think all you have to do is stick a wireless card in the Linux box you're using as a router, along with a regular NIC, so it can access both the wireless and wired networks. Properly configured, it will be a gateway from one subnet (wireless) to the other (wired) and to the internet. Check out the IP Masq. mini howto for more info on IP masquerading, and the route manpage for how to configure the actual routing.

    BTW, you can still use the Linux router as a normal desktop machine -- no need for a dedicated box unless you generate *lots* of traffic.

  • Won't work. Ethernet is baseband, i.e. there is no carrier signal that is modulated. It would be like an old spark gap transmitter and would probably destroy radio and tv reception in the area around it. Remember, a pulse has virtually infinite harmonics (I know that is oversimplifying) and an ethernet card is generating lots of pulses.
  • I have been working/playing with a bunch of wireless LAN cards recently. The way I did it was to use the Linux server/gateway as a router between the wired and wireless LANs. I personally use the Aviator Webgear cards (2Mb/s) because they are available for $149 at Frys for two PCMCIA cards and two ISA PCMCIA adapter cards. All works under Linux and can be interoperable with Windows. Be carefull of you are looking for inter-brand interoperability though. The avaitors are frequency hoppers and most others are direct sequence. I have had up to 4 aviators happily talking in ad-hoc mode (like a wired ethernet) and 5 lucent wavelan cards, even at the same time, in the same house. You do not need an access point for in-home use. BTW, for those in Europe (like me) the Proxim doesn't go through concrete floors very well, the aviators do. If you do this follow the ipmasq HOWTO but remember you need two sets of rules, one for the wired network and one for the wireless. As long as each device points at the IP address (wired or wireless respectively) of the Linux server/gateway everything should be fine. And to stop any trolls, you can do a search and replace for Linux with *BSD above if you wish. If you want to do this using a Windows server/gateway, you're in the hands of Microsoft. Good Luck.
  • Ive done somthing like this with a Wavlan
    the system consisted of
    -- One Windows NT machine
    -- One Win95 machine
    -- A Linux Box(doing ip masq for inet access)
    -- 3 laptops

    the linux box had a normal wavlan can and ran routed. The wired machines were on a subnet, and the wireless on another. Each laptop used the linux machine as their gateway.
    thats about it.
    email questions to andy@nethernet.com
  • Drilling holes to lay cable in your own home
    has to be one of the most fufilling experiences
    in the world, especially when you're done and
    have a shiny new 100mbit LAN and a cable modem/DSL
    on the end of it. :) Just drill surrepititiously
    in your apartment and you probably won't have
    an issue. One of the least obtrusive ways I found
    was to slightly bend the corner of a HVAC(heat/ventil/air conditioning)
    vent from below and slip some cat5 up through, lead it under the carpet along the wall,
    and right to my kitchen terminal. :)
    But then, my hub was in the basement where I had access
    to the ducts, too, and it looked like a spider's den of
    cables dangling -everywhere-. Had a nice effect on visitor, though.

    .head.
  • If he (she?) needed convincing that wireless would be easier, I think you just accomplished that. : )
    It sounds as though this is part of a house or other privately owned structure instead of a cookie-cutter apartment complex. If the landlord is a person instead of some company, why not approach them about "improving" their property for them for free? (much better than getting caught and evicted) Tell them it will help them to rent the place to another nice geek when you move out. If possible (check local building codes, including electrical) use some sort of conduit, like schedule 40 PVC or ,my favorite, Electrical Non-metallic Tubing, a ribbed flexible plastic tubing known as "smurf pipe" because of the bright blue color. That way, you can upgrade just by pulling wire or cable or fiber or whatever the "next big thing" is.
  • You say you are renting this place - a three level apartment (a basement and two above ground floors). You say you can't run wire because you are renting. I say you haven't tried.

    As someone who has lived in SEVERAL apartments, and is currently renting a house (with express permission to do damn near anything I wish, short of busting out a wall!), I can tell you it is EASY to run wire, even if you have to go through concrete.

    The thing is, you have to want to do it - rent a SawsAll and go for it! I have seen the "normal" maintenance guys tear the SHIT out different rooms in the apartments I have lived in (mostly for plumbing problems), and restore them to the way they were with hardly a seam afterward. If maintenance drones can do it - YOU CAN TOO! Learn how to do simple drywall repair, patching and plasterwork, and learn how to paint. I cannot tell you how many times I have "restored" an apartment I had "trashed" when I moved out - and got my deposit back, in full, EVERY time.

    You may need to cut and drill a bit, but it isn't that hard to route cable in an apartment. It become massively easier to do it if the place is built out of wood or concrete block (in the case of wood, drill and cut. For block construction, pull an outlet out of the wall, and see if the wires run down past the "floor" you are on, and follow them to where they are going - sometimes, you can find another outlet inline vertically with each other - count bricks!). If the apartment is a concrete box construction (massive walls and ceilings of reinforced concrete), then you will need a concrete drill. Pull back the carpet in a corner and go for it.

    In the end, when you move out, do what patching you need to - do it neat, and blend the paint. Ask what color paint they use (tell them you need some for touch up repair - sometimes they'll give you a pint), or take a sample and have it color matched. Or wait until they paint one of the apartments, then "walk in" on the paint crew and ask. Many times apartments and other rentals will use the cheapest stuff they can find (Conco Brand Cottage White is a favorite in my area).

    Final note - when you move out, close all drapes/blinds, and close all doors (cabinets, closets and interior). Do the inspection during late evening, on a Friday is best. This is so they won't bother to do too thorough of an inspection - and they may skip over some of the finer points, and miss others (got to get home, away from work, weekend is here). However, this in NO WAY should keep you from doing the best job you can repairing what you have done, so do that portion properly, without haste. Then blame anything that is noticed on a past repair.

    It can be done - I know, I have done it - YOU CAN TOO.
  • If I buy three wireless LAN equiped laptops (such as those ibooks or PCs with cards, whatever) and arrange them so that laptop A is at one end of a very long room, and laptop B is at the other end of the room, so that B and A *cannot* communicate, but I place C in the middle such that B and C *can* talk and A and C *can* talk -- does the obvious thing happen ?

    That is, does C begin re-broadcasting packets going between A and B so that they get to right place ?

    As I understand things, this is a software issue -- do the machines recognize when to configure themselves as routers ? If only some OS's or drivers do it, which ones ? If I install linux on an ibook or PC with the wireless LAN card, can I make linux do the right thing ?

    If there were two wireless ethernet devices on the machine in the middle, I think I could figure out how to make linux do this. But can linux re-route packets through a single interface device ? I know it is possible to re-route things heard on one device to be broadcast on another, since that is what my IP-masqing linux box connected to cable modem on one card and the apartment-mates machines on the other does.

    ZoomAir has something they call "AcessPoint Software" which does this on a machine with one wire card and one wireless card. Can this software be tricked to use a single wireless card as a bridge between two networks ? Furthermore, can you configure it to automatically recognize the situation in which it should start routing, and stop when it shouldn't ?

    I've been doing google searches -- does anyone have any URLs of where to start ?

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