I am working on a friends Mac. The Mac gets an IP address ok from a cable modem via DHCP. I put a Vonage router in front of it and it got an address from that. But I could not get to the internet. I turned off DHCP on the Vonage router and then static mapped the ip on the Mac. This worked for half a day. My friend shut down the Mac for the day. The next morning my friend powered up the Mac and there was no connection to the internet. I now have a couple of network connection profiles. Did it maybe go back to a default connection for picking the IP via DHCP? The cable company had her take the Vonage router out and connect straight to their cable modem and change back to DHCP. This got her back on the internet. I thought it could be the Vonage device so I put a Linksys router in front of it but again no connection to the internet using DHCP. A Windows laptop behind the Vonage device worked right away, ju. I am running a lot at you at once but wanted to cover all the troubleshooting I have done so far.
My big mystery is why it works with DHCP from the cable modem. If it uses DHCP from any other device it gets an IP ok but cannot talk to the internet.
Thank you.

You can modify the printer ip address via the CUPS admin page, but you will have to do this on each client.
Open your browser and type http://127.0.0.1:631/printers. You will see a page with each printer queue listed. For the printer/s you need to change, click on Modify Printer. You will have to authenticate as an administrator of the Mac (which I guess you are). Click Continue until you get to the Device URI page where you can change the ip address. Click Continue until you get back to the Printers page.
FYI - Can I suggest that you look using DNS names for the printers rather than IP addresses. That way if there is ever a need to change the address on your printers, you will never need to change the driver on the client..