Hello,

Here is my problem :
I need to install a 4G failover system on a network, but there already is a router, on which I have no control.
This router is also a dhcp server.

What I'd like to achieve is to put a Mikrotik router between this existing router and the LAN.
Is it possible to setup router os as a bridge, but with the capability of redirecting packets to another gateway in case of failure ?

Sorry if it isn't clear, I'm not a native english speaker, and sometimes, it's hard to find the right words...

Joris

It will be much simpler to use the existing router only to provide WAN uplink to the Mikrotik one and let the Mikrotik do the rest. Do you have any particular reason not to do it this way?

You're right, but I can't modify anything on the existing router, it is not mine, and I don't have the credentials :/
That's why I'm looking for an alternative...

But what I describe is an alternative - you don't need to change anything on the existing router, it will just provide an uplink and address to the Mikrotik, and the Mikrotik will take over the rest.

The LAN hosts receive not only their own IP addresses but also the IP address of the default gateway from the existing router. So the only way to let the Mikrotik act as a bridge would be to let it do so only while the primary uplink would be fine, but once the primary uplink would fail, the Mikrotik would have to reconfigure itself into a router, start to impersonate the IP and MAC of the existing router to the LAN clients and deliver their traffic via the backup uplink, but at the same time monitor the primary uplink via the existing router and once it would start working again, reconfigure itself into a transparent bridge again. It is doable, but somehow it seems much more complex to me as compared to a regular dual-wan configuration.

Thanks, I wanted to know if there was a simple way to do what I wanted to do, in order to keep the same LAN address :)
No I know that there is no simple way to do that, so I did exactly what you advice.

Joris