Comments on: Dual Internet Connections: How to Swap ISP’s Smoothly on a Mixed Platform Network

By: Cheap DSL Internet

Cheap DSL Internet — Fri, 25 Mar 2011 01:57:25 +0000

Thank you for this command: ipconfig /flushdns

It was exactly what I needed to switch the DHCP.

By: Ivantee

Ivantee — Thu, 02 Apr 2009 02:17:02 +0000

We’ve had trouble with two of our routers during the last month as well – the old Asanté FR1104-G just went the round filing cabinet after years of loyal service while D-Link’s DVG-1120 came back to life after a hard reset and multiple reboots – so I quite like the idea of two entirely self-sufficient networks.

By: Stuart

Stuart — Wed, 30 Jan 2008 11:54:57 +0000

We operate a small internet cafe and the use of the /flushdns and the single cable swap is useful info. thanks.

running a seperate dhcp server on the lan is interesting as technical fun and i’m not convinced but i will try it, theres an unused old router in the junk box.

maybe it will take years for a system to evolve that solves the problem of automatic internet route switching. such that if our ADSL drops out we can at a touch of a button send the traffic up our backup connection.

do tell if anyone has success with a linux implementation. would be great if it came with a setup tutorial.

By: alec

alec — Thu, 03 Jan 2008 18:53:02 +0000

Thanks Bill. That’s a good idea.

On the other hand, when we get in some new routers in which we feel fully confident, that’s not a bad idea at all. There will be some small traffic slow down as on the DSL line, the firewall is built into the modem and we will effectively be running a double firewall.

In terms of reconfiguring the NAT router, we wouldn’t have to do so as for the cable broadband we are bound via MAC address and for the DSL line we are getting a straight DHCP connection from the firewall/router (which already does the PPPoE binding).

Worth testing for performance.

And as you point out, at that point we can just swap a single network cable going into the router and keep working. There will be no DNS or network renewal needed.

Great suggestion. We won’t get load balancing but we’ll get near instant redundant swapover.

By: Pecos Bill

Pecos Bill — Thu, 03 Jan 2008 18:41:25 +0000

It would seem to me that you could avoid the entire renewing lease problem by running a local NAT router with 10. or 192.168. addressing and DHCP. Both ISP routers would be alleviated of that duty and just pass traffic (bridge mode). Not having two setups like that, I can’t say I’d tried it.

You would still have to swap modems and the NAT router would have to be reconfigured with a new WAN IP config. For a very small corp, it might not be worth it.

For windows, you can do in “DOS” nka command line:

ipconfig /release
ipconfig /renew

but it doesn’t always work. Sometimes a reboot is required.