Dual Internet Connections: How to Swap ISP’s Smoothly on a Mixed Platform Network
January 2nd, 2008
We have occasionally - say about once a month - had small problems with our cable internet (Chello.sk). We've been lucky - the longest we've been down is one and a half hours and most of the time it's less than this.
Even a single day with internet down for a whole day would cost the company three times more in lost productivity than the cost of the second high speed connection for the year.
So we've done what every modern business should do. We now have redundant high speed internet from T-Com.
Which is a good thing as our cable internet is down today. But no big deal, I just swapped the router over to the DSL connection and we were all ready to get back to work. Well, almost.
With Mac OS X, switching over from one network connection is as easy as renewing your DHCP lease in the Network preference pane - the OS will usually do so automatically.
mac os x switching network
With Windows, it's a little more difficult as the computer will not want to switch over automatically, even if you open up the Local Area Connection Status and press repair.
That's not enough. After some positive messages, you will get an error saying that Windows is unable to repair DNS.
The simple but tiresome solution is to restart your computer. No big deal for one computer but for seven, a real pain in the neck.
There is a faster way. Open up Start -> Run and type:
ipconfig /flushdns
Your connection should be immediately live.
So now we have redundant internet for the whole office with just swapping over a single cable.
In terms of a longer term solution, we are thinking buying a load balancing router.
Unfortunately the reviews of all of them from the
D-Link DI-LB604
whether the D-Link DI-LB604 4-Port Load Balancing Router or the Linksys RV082 have been so rotten that there doesn't seem to be any point in buying one for less than a thousand dollars. That's a lot of money for about $50 worth of hardware. Especially hardware which doesn't work very well.
or the At that price, it makes more sense to build your own load balancing Linux server. At least that way, one is future proofed. Load balancing routers are in their infancy and have to get better and cheaper over the next two years. I have no interest in paying the early adopter tax and then struggling with a shoddy solution.
What distribution or software to use. Reliable sources (tech support at Cartika webhosting) suggested doing it the Untangle Gateway Platform - which is free for DIY or $25/month with full support. Another well-known free alternative is pfSense (Wikipedia info). For background, read this good IBM article on setting up a network router on Linux.
The issue with any of this setup is the hours it will take to get it working properly. Later this month, I'll probably have our new IT guy Alexander sit down and figure out Untangle on an old server from Vienna. If any of it works, I'll let you know.
In the meantime, just remember cable swap and ipconfig /flushdns.
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