Multiple Gateway in preparation for ISP switch

RouterOS General
1

I have a remote customer who I would like to prepare for an upcoming ISP change which will change the IP of his modem and I have a question about having two IPs listed as “gateway”. I won’t be able to be physically present when the change over occurs so I’m trying to figure out how I can have everything set up so the customer can just unplug the one modem and plug in the other one. Before the switchover occurs I will know the IP address of the new modem.

I’ve read topics on this forum about people using more than one gateway at a time and it appears that having two gateway IPs listed, one reachable and one unreachable is not an issue. So it appears I could configure the customer’s router with both modem’s IP addresses as gateways so while it’s functioning on the current ISP’s modem it’s configured to also work with the new ISP’s modem.

While the router is still connected to the current modem, I plan on adding the new modem’s IP in his RB-750 as another gateway IP (and add the appropriate IP address in “Addresses” for ether1-gateway). My understanding is if the router has the current ISP (ISP “a”) modem’s IP as a gateway, and the new ISP (ISP “b”) modem’s IP as a gateway, then when the router is still connected to ISP a’s modem, ISP b’s modem’s IP will be “unreachable” and ignored. When the router is physically disconnected from ISP a’s modem and connected to ISP b’s modem then ISP b’s modem’s IP address will become reachable as a gateway (and ISP a’s modem’s IP will become unreachable) and traffic should begin flowing through ISP b’s modem.

Is there any reason why this would fail?

Thanks!
Greg

2

It sounds like you have the right idea. You might also want to look at route distance.

http://wiki.mikrotik.com/wiki/Manual:IP/Route

3

You will want to set check gateway to ping when you add the route, so that it knows to not enable it when you add it into the system. Then have the same thing set for the current default route. The check gateway function pings the next hop (the default gateway) to see if it is reachable.

The other thing that you can do is set up a script with a route on a different routing table, and have it ping out that routing table, once it can successfully do so, it can then enable the new route and disable the old.

4

Thanks so much guys! I really appreciate you sharing your experience and expertise.

Greg