I just picked up Dave Winer’s question about how to set up his home network with dual Internet access points. There were several commenters that suggested using dual WAN interfaced routers to aggregate the connections and that is a viable approach. Dave seems to want something simpler. A setup where he can switch back and forth between the two Internet connections when he decides he wants to do that. There are a couple ways to go, but I think the one illustrated below would be the simplest.

In the diagram, I have his two Internet gateways set up as 192.168.1.1 and 192.168.1.2. They are on the same non-routable network of 192.168.1.0/24 (that’s a subnet mask of 255.255.255.0) which makes switching between the Internet gateways fairly simple. One device needs to be set up on the network as a DHCP server ( or you could manage IP addresses manually I suppose ). In the diagram I have it as the wireless access point, but it could be either of the routers or the server for that matter (Though the server wouldn’t be my first choice for reasons that will become clear). The other nicety for a DHCP server would be one that allows static mapping of DHCP addresses so you could do 1 to 1 correlations where the MAC address of machine1 corresponds to 192.168.1.5, etc. This makes sure that the same machine always gets the same address. I would also set up the DHCP server with a fairly short lease time, say 5 minutes or so. One of the parameters that can be distributed by a DHCP server is the default gateway for the network, or the path to the “outside” of that network. In this case, that is the path to the Internet. For the network illustrated, that gateway would be either 192.168.1.1 OR 192.168.1.2, depending on which interface Dave wanted to use at that time. Simply changing the gateway setting in the DHCP server would automatically re-populate the path to the Internet on all of his machines (Including his server if it was set up with a static DHCP mapping) at 5 minute intervals (or whatever DHCP lease time he wanted to use).

The reason for not making the file (or web) server also serve as the DHCP server is that you don’t want a computer to get it’s DHCP information from itself. It just won’t work.

The upside to this whole thing is that his static drive mappings to the various machines in his house, as well as any port forwarding information on his routers will stay the same, no matter which Internet gateway he is using.

Technorati Tags: Dave Winer, Internet, Networking, Scripting News

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