How to set-up my home intranet using 2 different ISP's ?

Question

I have had so much trouble recently with my main (8 years now!) internet provider "ABC" (not the real name) Cable Modem here in Belgium that I made the decision to pay another bunch each month to have a second ISP for my home and home office. "XYZ" (also not the real name) will start on Monday 26 July. It is a DSL line, linked to my TV and fixed telephone. Great, except I'm not really sure how to set-up this 2nd ISP.
First, I want this 2nd ISP to (at least for now) be an emergency backup. So if ABC shuts down again (as it has done a lot recently, but no technician can come until 30 July- poor service there!) - I want to immediately be able to use the XYZ server.
OK the XYZ has a kinda built-in router in that the DSL Modem has built-in WiFi and also 2 cable to computer out ports. I believe I can first just configure the WiFi: Apparently I have to attach my MBP-13" via cable in order to change / add a security code; maybe change the name of the WiFi from its default "XYZ-WiFi" (not the real name) to something I want like SteveXYZ and then add a security protection code.
But how to configure my eMail using MAIL? And can I still keep getting my eMail from my main "[email protected]" (not the real address) even when connected via XYZ? And what about SENDING from ABC when connected via the server XYZ?
Also: I currently have my ABC Modem going to a 4-port D-Link DI604 Router. From there, one cable goes to my MacBook Pro-13"; one to the Apple LaserWriter 12/640PS (great printer- 13 years old and still super); one to my Canon MP640 and one upstairs to another router: D-Link DIR-635 wired and wireless. From there, one cable goes to my wife's eMac; and another is available for guests; another unused and then the WiFi for when I compute in the garden and of course for my iTouch.
So now let's say that on 28 July the ABC is down. Ideally I'd like to pull the cable from the ABC Modem that goes into the DI604 Router and plug-in a cable going to the XYZ DSL Modem and voilà have internet back via my backup XYZ. BUT can I print? Do I have to reboot the Router since it will have to reassign those 192.168.0.123 type numbers, won't it? (I believe those numbers are called the "IP Addresses").
Thanks for any comments or references here.
Best regards,
Steve Schulte
Wednesday 21 July 2010

Answer 1

In your Network Preferences you can set up more than one method of connecting - i.e., Airport, Ethernet, Dial-up (heaven forbid). If, for example, you place Ethernet at the top of the list, then Airport, your Mac will try to connect to Ethernet first. If it can't, it will fall back to Airport.
So if you can have Airport connected to one ISP and Ethernet connected to another, you will be able to pick one or the other by imply pulling the Ethernet cord. What you can't do is set up two Ethernet connections (or Airport connections) each with a different ISP (though if I read you aright this isn't what you want anyway).
Another method is to set up 'Locations'. You could set up one with Airport only, and one with Ethernet only, and switch between them using Apple Menu>Locations: this would save you physically pulling cables and is just as quick, it takes only a few seconds.
As to mail, it depends on your ISP. Some ISPs demand that you are connected directly to them to send mail, and possibly also to receive mail: some rely entirely on the password. In the latter case you can use the same settings in both locations or methods: in the former you can't get round that - if you're not connected you can't send/receive as relevant.