I’m a big fan of redundancy when it comes to Internet connectivity. Sometimes your provider has maintenance, or random cablemodem reboots, or routing issues. And sometimes the hardware fails… I once had an enterprise colo site go down because, of all things, a SFP module for the Internet uplink failed.

There are two roads you can go down…

So for quite a while I’ve had two Internet connections at home. The primary one is ADSL2+ through Sonic.net, a local Bay Area ISP who offer service limited only by the laws of physics. With Annex M turned on, I get about 25mbit down/4mbit up — Annex M trades a chunk of download speed for a smaller chunk of upload speed, and with things like Bitcasa, Dropbox, and so forth, upload speed becomes more important.

My secondary connection is a Comcast cablemodem… we have to have television for the little one anyway, so the additional cost for 25mbit-ish cable service is negligible.

For the longest time, I had separate wireless routers behind each connection. Sonic was the default, but if I had issues with that connection or just wanted a full 25mbit (or 15mbit at the time), I’d switch my laptop to the other wireless. What this meant was that most of the time, I had a 25mbit connection sitting idle.

As I mentioned, the cablemodem service could be justified away as free, if I accept the usual price for a modest tv package, and remember to renegotiate every 6 months or so. But still, it seemed like a waste.

Throwing hardware at the problem sometimes helps…

So I got the new-at-the-time Cradlepoint MBR-1200. This is a Wireless-N router that supports up to 5 broadband wireless modems (USB and ExpressCard), as well as up to two Gigabit Ethernet WAN connections. It will load balance across them, or a common option is to have the broadband cards serve as failover in case the wired WAN fails. So I set up the two connections that way, each getting DHCP settings from the respective providers, and started using it.

I found the connection was not reliable in load balancing mode, primarily due to DNS. Generally an ISP allows its customers/netblocks to use its resolvers, but doesn’t leave them open to the world. So if the router got one provider’s DNS, but the connection went out the other provider’s line, I’d have problems resolving DNS records.

I didn’t think about it at the time–just went back to the manual failover method with separate networks–but when I found a good deal on a Cisco Linksys RV042 dual wan router, I started thinking about it again. About that time I’d started using OpenDNS, a third party DNS provider that provides metrics on your DNS use.

Or maybe throwing the cloud at it will help?

Then it hit me. Third party DNS would get around the split-brain networking issue I’d been experiencing before. I set up the RV042 with Comcast on one side and Sonic on the other, plugged in the OpenDNS resolvers in place of the provider DNS, and gave it a try. It worked.

I have still run into at least one problem that can be traced to the dual WAN configuration. Vonage, my phone service, gets terribly confused if client connections come in from multiple IPs, and was making me log in again for every frame and page I viewed. I haven’t seen this for any other sites, including banking and e-commerce. The solution for this was to set a static route to their subnet through one WAN connection, and now I can view my account again.

And there are two other things I’m disappointed with in this configuration. One is that the RV042 is 10/100, and in theory Comcast could go faster than that would allow. The other is that the RV042 is too old for IPv6, but as I recall the Cradlepoint routers don’t support IPv6 either (even the ones that didn’t EOL last year like mine, sigh), so it’s not a specific pain to the RV042.

I expect that when Sonic.net comes out with native (non-tunnel) IPv6 I will start looking around again for a load balancing option. Maybe Peplink Balance 20/30 would do the job (100mbit, but IPv6 is supported even in the lower-end models).

As an aside, there are newer versions of the hardware above… and the links do add to my toy budget, if you choose to use them.

• Cisco Small Business RV042G Dual Gigabit WAN VPN – newer Gigabit version
• Cradlepoint MBR1200B which as I recall supports link affinity and WiFi-as-WAN but still not IPv6

Have you done small network load balancing? What caveats and eurekas did you run into? And what hardware do you recommend?