Bridging two wireless networks

Originally Published 2004-03-02 12:24:45

Found on comp.os.ms-windows.networking.windows via google groups. Poster was anonymous ("Jim"). The most complete discussion on the topic that I've seen.

--Ok, hold on...

So you each have and will continue to maintain your own broadband access.You just want to "bridge" these otherwise disparate networks for some filesharing. Each of you has a 24/7 PC for Internet routing purposes (which youintend to maintain), but no hardware routers are currently in use, justswitches.

Solution # 1:

Peer-to-peer. This is by far the simplest and cheapest solution, theconstraints are range and antenna placement. What you can do is installwireless network adapters (I prefer USB-based, one w/ a 6' cable is ideal)on each network (config'd for adhoc mode, not infrastructure). NO AP (accesspoint) is involved. I would place them on your respective 24/7 PCs, sincethese already provide routing services to your respective Internetconnections. It should be a trival matter to ADD the remote networks tothese routers. Of course, you could use ANY PC, the 24/7 PCs just make sensesince they're always available and already have routing software. I can'tspeak to the flexibility of ICS in this matter (you didn't mention yourcurrent software), I don't use it myself, I typically use a hardware router,or when software-based, WinGate, WinRoute, etc.

Again, it's a matter of range. I find that even a few inches in theplacement of my antenna can be the difference between connecting and NOT, soI tend to stay away from PCI card and PCMCIA solutions. IMO, USB-based w/cable works best, I have the flexibility of working on almost any PC orlaptop w/ freedom of movement.

SPECIAL NOTE: On a peer-to-peer setup, you might want to be especiallycareful in comparing products. Some brands are notoriously BETTER in termsof range than others, so it might be worth a few extra $$$ to get a pair ofthese HIGH-END wireless adapters. Check the specs and visit some hardwarereview sites for comments (which you should be doing for ALL the equipmentmentioned here anyway!).

Solution # 2

Infrastructure (AP-based). In this case, you use two APs (access points),each patched into an available LAN port (wired) on your respective LANs. Inturn, the APs are bridged to each other wirelessly. The advantage of thissolution is RANGE and SIMPLICITY. It's the functional equivalent of using acrossover cable. The APs simply move traffic back and forth between theswitches. For all intents and purposes, you have a SINGLE, LOGICAL network.It can get more complicated, depends on what you want. For example,depending on the AP purchased and features, it may come w/ its own DHCPservice, firewalls, etc., thus you could each maintain some isolation, somecontrol over your respective networks, even use different IP addressingschemes. You would have to resolve the issue of whether you have a shared IPpool, which may have to be negotiated w/ the DHCP services provide by theAPs (if featured), or subnet your networks to avoid potential IP conflicts.None of this any different than if you were connecting "wired" networks, sono point in elaborating here. Sometimes people want separate networks andthus "route", other want ONE network, thus "switch". The wireless issues arebasically the same as wired once bridged. Depending on AP product, youroptions may be limited, so check carefully (of course, more features == more$$$).

In general, an AP-based solution is more likely to give you greater rangesince that's it's primary function. Since it's patched to your switch, youcan also have a VERY long lead, anything within the Ethernet spec (~300 ft,as I recall). In other words, you don't become BOUNDED to the placement ofyour PC as in solution #1, instead, it's a function of where your switch isPLUS the distance of the CAT5 cable. You can stick the AP up high, out awindow, whatever makes sense. Considering that BOTH of you could do this,you can potentially deminish the PHYSICAL distance between the APssubstantially, thus increasing the EFFECTIVE range. And you can add as manyAPs as you need to extend the range even further, creating a "chain" of APs.A very powerful solution. However, they can get expensive for thefull-featured models. That's why I suggested the peer-to-peer solutionfirst, it may work just fine, especially given the distances mentioned,line-of-sight, no other 2.4GHz interference (assuming you go 802.11b), andnot many obstacles. It's worth trying anyway, esp. since you have all theother necessary elements established (24/7 PC, routing software, etc.). Acouple of D-Link DWL-120 wireless adapters here in the U.S.A. might run$20-40 USD, either after rebate if new, or used off eBay. An AP, incontrast, could run from $80-200 (or more) USD depending on features.

Btw, the peer-to-peer solution's range can be extended considerably (haveheard of 3-5 miles in cases!) using after market antenna, concentrators(ideal for line-of-sight), etc. There are even websites dedicated to the"pringles can" solution (search Google). But don't underestimate the rangeof basic 802.11b wireless (esp. w/ line-of-sight), there's a reason hackersare continually invading unsecure corporate networks from basic, unenhanced802.11b wireless laptops on park benches ;)

Solution # 3

APs (infrastructure mode) + wireless adapters. In this example, you maintaincompletely separate networks and allow each other access via your respectiveAPs like any other wireless clients, such as laptop roamers. This config isclearly the most expensive so far (just more equipment), but highlyflexible. You could isolate access to the other's network to a single PC,i.e., wherever you wish the wireless adapter to be installed. Why might youconsider this? Because I'm not sure that your APs in solution # 2 wouldallow bridging *AND* local wireless access (roamers via infrastructure mode)AT THE SAME TIME. Maybe most APs do, maybe not, again APs vary widely as tofeatures, you need to check. But if you went w/ solution #2 and bridged,roaming might not be supported. Using the solution proposed here, you arecapable of supporting BOTH your neighbor and roaming clients because BOTHAPs are running in infrastructure mode, NOT bridged, so EVERYONE is happy.But of course, roaming may not be of concern to you, it's your call. Youcould always replace your switches w/ wireless routers sometime later toresolve that limitation. Just something to think about.

Solution # 4

Wireless Routers + AP. You could replace your existing switches w/ wirelessrouters (w/ integrated switch). Or, just supplement each of your currentswitches with a wireless router (simple crossover cable will do). Then useONE (possibly TWO or more if range is insufficient) APs to bridge them. Mostconsumer oriented wireless routers (e.g., D-Link DI-614+, Netgear MR814) doNOT support bridging, a requirement for your purposes. But they DO support abasic, simple AP for roaming wireless clients. The fact that these deviceshave LIMITED AP functionality is what keeps the prices down! But they'restill great products, they give a small, local networkswitching+routing+wireless in ONE, neat little package. Frankly, I stronglyrecommend hardware-based routers over your current software-based router.You created a dependency that has many negatives, like time-to-boot, heat,power usage, probably security vulnerabilities, cost of licensing, amongothers. In the end, it's usually cheaper and easier to buy a hardwarerouter, at least here in the U.S.A. (running $40-50 USD). If you can believeit, I recently picked up a Netgear MR814 for a measly $20 USD.

The only remaining issue is, how to bridge them. That's why you need atleast ONE AP (note how solution #2 required TWO APs, because you didn't havethe wireless routers as in this solution to BOOT the process). So a singleAP may be sufficient to bridge the wireless routers (if not, add more), andcould EVEN be placed mid-way (which may be ideal, depends on conditions),like at a third (otherwise not-involved) neighbor (or maybe the pole youspoke of, just kidding)! Or you can simply patch it to one of the twonetworks over a LAN port, and your neighbor's AP can reach it in bridgingmode. Your choice.

The nice part here is that you've greatly improved your local LANconfiguration (IMO) with the wireless routers, irrespective of anythingelse. So even if at some point, this relationship breaks down, neighbormoves, etc., you still have use of your investment, just add wirelessadapters and your off. The additional costs comes in the way of that AP,something you could probably agree to split, and you're done(equipment-wise).

Solution # 5

Wireless Routers + wireless adapters. Essentially, this is a hybrid ofsolution # 1 and #5. It assumes the range is sufficent with wirelessadapters as in solution #1 but drops the APs of solution # 4 (to save $$$),for the less expensive wireless routers (as you recall, switches w/ low-endAPs).

By now, I hope you're getting some of this. You're just allowing access toeach other's networks as roamers, hopefully in range like anyone visitingyour home w/ a wireless laptop. Actually a very simple config, probablyeasier to understand and configure than any other solution here. No APs, nobridging, no reconfig of software routers (no routing at all frankly, you'rejust PURE wireless clients to each other networks). It does limit you to aSINGLE client machine, however, unless you are willing to introduce routingon the machine w/ that wireless adapter! In that case, you're back tomanaging a software router again (maybe ICS, or maybe a simple bridgeconnection under WinXP will do, not sure), which sort of defeats the purposeof having invested in wireless routers. This solution works best IF youreally only need access to the other network from a single machine. It'ssimple, effective, but limited.

Summary

That's basically it (as I see it), there are lots of nuances, of course. I'mgiving a BROAD picture, there are even competing wireless standards, withvarying range and capabilities. For this discussion, I've assumed 802.11b(2.4GHz) wireless since it is cheapest and readily available. It's limitedto 11mbps (by spec), but actual is closer to ~2-4mbps (btw, SHARED,HALF-DUPLEX), under good conditions. Under stress, (extended range, other2.4GHz devices, other wireless networks, even weather), range may drop to1mbps or less. I've already outlined possible workarounds, from third-partyantenna to APs. Then there's 802.11a, its theorectical throughput issubstantially higher >50mbps (actual, probably ~20-25mbps under ideal conditions), but it achieves that at the expense of range. It may notfulfill your needs UNLESS you supplement it w/ range extending solutionssimilar to 802.11b. And then there's 802.11g (not even a standard as yet),which is backward compatible w/ 802.11b (note, 802.11a is NOT backwardcompatible w/ 802.11b, one of the reasons it's faultering in the marketright now). Confused yet? We're now seeing dual-mode (802.11a/b) and eventri-mode (802.11.a/b/g) APs, wireless adapters, and routers!!! Even moreexpensive, but these provide LOTS of options, esp. if you're not sure whatwill work best for your circumstances.

In the end, YOU will have to decide what makes sense for your circustances,and you may make a mistake or two along the way, be daring and at least tryit. A little experience and you'll probably come up w/ your own uniquesolution. But almost ANYTHING will be better than trying to lay down CAT5between your homes, that solution is problematic.