# Ethernet A/B switch? **URL:** \ **Category:** Factual Questions\ **Created:** [February 16, 2011, 8:09pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621 "2011-02-16T20:09:12Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [February 16, 2011, 8:09pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/1 "2011-02-16T20:09:12Z")
We have two broadband connections coming into the house.[sup]\*[/sup] When the primary connection goes down, I’d like an easy way to switch everything over to the backup connection. Right now, I’d have to swap the cable running from the modem to the router. Doesn’t sound like a big deal, but it involves a lot of climbing, contorting, and consternation. Instead, I’d like to run the cables from the cable modem and the DSL modem to an A/B switchbox with one cable going to the router. But searching for switch (and variants) brings me to hubs, routers, etc.—I can’t find an A/B switch. Do they make such a thing? One that won’t cut down on signal strength? [sup]\*[Original thread](http://boards.straightdope.com/sdmb/showthread.php?t=577370) on two Internet connections. I haven’t given up on finding a load balancing router, but so far the price points and other issues have blocked progress. I’m currently looking at a [Cisco RV042](http://www.newegg.com/Product/Product.aspx?Item=N82E16833124160) for ~$150, but I can’t get Cisco pre-sales to help figure out if it will do what I want.[/sup] ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 16, 2011, 8:38pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/2 "2011-02-16T20:38:35Z")
I’ve never seen such a thing - ethernet connections aren’t really designed to be switched in that sort of way. ETA: wrote this before noticing the subscript: If you got a dual WAN router, you could configure it to bridge the connections (and you would experience a faster connection when both broadband lines are working) ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [February 16, 2011, 8:39pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/3 "2011-02-16T20:39:44Z")
It may be possible to have them both connected at the same time and the computer would chose which ‘gateway’ it wants to use. I did this back in the dialup days, where I would use a land line for one connection and (the slow old 14.4kb/s) cellular for another. When I had them both on I would have the web configured to use one connection and outlook express to use the other. Also I got netscape to use one and ie to use the other. ---
**Author:** ![Palooka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/palooka/32/2902_2.png) [@Palooka](https://boards.straightdope.com/u/Palooka)\ **Post date:** [February 16, 2011, 8:41pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/4 "2011-02-16T20:41:39Z")
They’re much easier to find if you call them [RJ45 switches](http://www.monoprice.com/products/search.asp?keyword=rj45+switch&x=0&y=0). ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 16, 2011, 8:58pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/5 "2011-02-16T20:58:46Z")
Blimey. I’m really surprised they exist at all. Physical switching seems so incongruent with ethernet (I wonder if those devices are intended for something other than networking - for example, switching peripherals that happen to use patch cables for comms, but not using network protocols) ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [February 16, 2011, 8:59pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/6 "2011-02-16T20:59:50Z")
> [@Mangetout](#): > > I’ve never seen such a thing - Ethernet connections aren’t really designed to be switched in that sort of way. Is there a downside to that kind of switching? Or is this just a rare idea? > [@](#): > > ETA: wrote this before noticing the subscript: > If you got a dual WAN router, you could configure it to bridge the connections (and you would experience a faster connection when both broadband lines are working) I’ve been on the phone with Cisco for the past forty minutes or so. The RV042 could do almost everything, but it won’t necessarily tell us when one connection is down (it’s in the logs, but no notice is sent), and it’s still an open question as to how it will manage the bandwidth (one connection is +/- 20Mps, the other is +/- 4Mps). The tech also said some VOIP devices have a problem with load balancing routers. So it may be a way to go, but it’s still not standing out as the definite way to go. > [@Palooka](#): > > They’re much easier to find if you call them [RJ45 switches](http://www.monoprice.com/products/search.asp?keyword=rj45+switch&x=0&y=0). I heart Monoprice! That’s another thing … a $150 router (with small learning curve) or an $8 box. Since the VOIP is connected to the DSL line and the rest of the network is on the cable, we’ll always know fairly quickly if one line goes down. And shunting the VOIP to the DSL line means we can down/upload on our main connection with no impact on call quality. A second A/B box will make it easy to switch the VOIP to the active connection, too. ---
**Author:** ![arseNal](https://avatars.discourse-cdn.com/v4/letter/a/ecae2f/32.png) [@arseNal](https://boards.straightdope.com/u/arseNal)\ **Post date:** [February 16, 2011, 9:01pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/7 "2011-02-16T21:01:33Z")
Never tried using a switch for ethernet like that, I suppose it could work. But your router might not be able to cope with the underlying incoming WAN connection just being switched under its nose like that. You might need to reboot it. Regarding dual wan routers, you need to decide if you want failover only, or failover and loadbalancing. Having both will cost you more. As to the RV042 you are looking at, here is a thread where someone struggled to get failover working but eventually did. However, the trick he used to properly detect failure on the primary WAN port seems goofy to me. > **[RV042 - Best Way to Setup Dual Wan - Linksys | DSLReports Forums](https://www.dslreports.com/forum/r21102328-RV042-Best-Way-to-Setup-Dual-Wan)** > > Forum discussion: I just purchased a RV042 for fail-over internet. I have two ISPs, and if one goes out, I want the other to kick in. I'm having two issues. The first is that when testing, if I unplug one of the internet modems the RV042 doesn't... ---
**Author:** ![arseNal](https://avatars.discourse-cdn.com/v4/letter/a/ecae2f/32.png) [@arseNal](https://boards.straightdope.com/u/arseNal)\ **Post date:** [February 16, 2011, 9:08pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/8 "2011-02-16T21:08:24Z")
20 mbps vs 4? Only an extremely intelligent loadbalancer (read: $$) would be able to get you any worthwhile gains with that setup. Any time it switches you over to the 4 for load balancing purposes would probably actually make what you’re doing slower than if you just used the 20 for everything. I’d forget trying to loadbalance. Your choices, IMO: 1. research a simpler failover-capable router (read reviews etc where people were unambiguously successful with it). The RV042 might be it, or there might be other tried and true ones that everyone uses (I’ve never really looked into it). 2. your ethernet switch idea. Heck, for $8, you have nothing to lose trying this route anyway. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [February 16, 2011, 9:12pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/9 "2011-02-16T21:12:05Z")
> [@arseNal](#): > > As to the RV042 you are looking at, here is a thread where someone struggled to get failover working but eventually did. However, the trick he used to properly detect failure on the primary WAN port seems goofy to me. > > [http://www.dslreports.com/forum/r21102328-RV042-Best-Way-to-Setup-Dual-Wan](http://www.dslreports.com/forum/r21102328-RV042-Best-Way-to-Setup-Dual-Wan) That’s really highlighting the time-cost of trying to go load balancing. Besides the $150, there is the potential for all sorts of hassles – and for what? The primary cable connection is more than fast enough for the foreseeable future (and we do a lot of movie watching in the den, music streaming, etc. in addition to our office work). Jumping through hoops to add about 4Mps to it seems like it might be more touble than it’s worth. As a tinkerer who builds all of our machines and whatnot, passing over a chance to learn and add shiny hardware is intuitively difficult, but in the end, I’m not seeing the overall benefit. As for how AB switch would work, since I’d have to get up to make the switch, restarting the router shouldn’t be a big deal. I have the main power switches on remote cords as it is to make restarting easier. ---
**Author:** ![arseNal](https://avatars.discourse-cdn.com/v4/letter/a/ecae2f/32.png) [@arseNal](https://boards.straightdope.com/u/arseNal)\ **Post date:** [February 16, 2011, 9:21pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/10 "2011-02-16T21:21:49Z")
> [@Rhythmdvl](#): > > That’s really highlighting the time-cost of trying to go load balancing. Besides the $150, there is the potential for all sorts of hassles – and for what? The primary cable connection is more than fast enough for the foreseeable future (and we do a lot of movie watching in the den, music streaming, etc. in addition to our office work). Jumping through hoops to add about 4Mps to it seems like it might be more touble than it’s worth. As a tinkerer who builds all of our machines and whatnot, passing over a chance to learn and add shiny hardware is intuitively difficult, but in the end, I’m not seeing the overall benefit. Actually, the thread I linked to involved the user trying to get **failover** working, not **loadbalancing** , which is the distinction I’m trying to point out. In my second post I did state what you said as well. It’s most likely not worth it to try to **loadbalance** a 20 mbps connection with a 4. Do automatic failover only, or just go for your switch idea. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [February 16, 2011, 9:33pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/11 "2011-02-16T21:33:06Z")
Thanks. Your second post came in while I was writing, so I hadn’t seen it before I posted. We don’t do anything critical internet-wise here (other than being able to keep working once we recognize a connection went down), so automatically managing failover isn’t all that needed. My original (linked in the OP) thread was my introduction to dual-WAN routers. If the price point and ease of integration was different–and the loadbalancing would have effectively created a +/-24Mps connection, that would have been a way to go. But for 8-16 bucks, the switches are the way to go experimentally. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [February 16, 2011, 9:55pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/12 "2011-02-16T21:55:25Z")
_Years_ ago, we used a similar A/B switch to share parallel printers between two computers. (This was before Ethernet was easy.) The manual A/B switches worked fine for the dot matrix printers, but when we wanted to share a laser printer, we were told (either by the switch manufacturer or the printer manufacturer) that manual switches were a bad idea as the voltage spike could damage the printer. So we ended up using automatic switches. So you might want to be careful. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [February 16, 2011, 10:02pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/13 "2011-02-16T22:02:56Z")
Yikes. Is there anything I can do about that before risking the router? Where would I start looking? A cursory search shows a couple [RJ45 surge protectors](http://www.google.com/products/catalog?q=rj45+surge&hl=en&client=firefox-a&hs=8YV&rls=org.mozilla:en-US:official&biw=1130&bih=633&prmd=ivns&um=1&ie=UTF-8&cid=7254209821917936566&ei=s0hcTai1DISclgf6zs3jCQ&sa=X&oi=product_catalog_result&ct=result&resnum=1&ved=0CHAQ8wIwAA), but how do I know they’re needed? ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [February 16, 2011, 10:15pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/14 "2011-02-16T22:15:12Z")
If you shut down the router and the cable modems before switching the connection, that would be safe. But it might be inconvenient. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [February 16, 2011, 10:18pm UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/15 "2011-02-16T22:18:51Z")
Some higher-end products (liek SonicWall firewall routers) allow for dual WAN and failover. Not sure of the exact models, considering it’s about $40 for a small home router vs. several hundred for a Sonicwall. However, if you can channel your inner nerd, you can set up a Linux firewall router with two network cards, one for each service, and set the relative weights (costs) of the two connections so unless the link is down, the preferred route is the faster one. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [February 17, 2011, 1:57am UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/16 "2011-02-17T01:57:48Z")
> [@Rhythmdvl](#): > > Yikes. Is there anything I can do about that before risking the router? Where would I start looking? A cursory search shows a couple [RJ45 surge protectors](http://www.google.com/products/catalog?q=rj45+surge&hl=en&client=firefox-a&hs=8YV&rls=org.mozilla:en-US:official&biw=1130&bih=633&prmd=ivns&um=1&ie=UTF-8&cid=7254209821917936566&ei=s0hcTai1DISclgf6zs3jCQ&sa=X&oi=product_catalog_result&ct=result&resnum=1&ved=0CHAQ8wIwAA), but how do I know they’re needed? Unless you are running Power-over-Ethernet, I don’t see how switching the cables could possibly cause any damage - Ethernet is transformer-isolated, and carries no DC bias. ---
**Author:** ![andrewm](https://avatars.discourse-cdn.com/v4/letter/a/c57346/32.png) [@andrewm](https://boards.straightdope.com/u/andrewm)\ **Post date:** [February 17, 2011, 2:46am UTC](https://boards.straightdope.com/t/ethernet-a-b-switch/571621/17 "2011-02-17T02:46:44Z")
> [@Palooka](#): > > They’re much easier to find if you call them [RJ45 switches](http://www.monoprice.com/products/search.asp?keyword=rj45+switch&x=0&y=0). Yep, they exist. I use them, they seem to get the job done. I don’t love the idea, but sometimes you need physical switching.