Hello guys,nice to meet you.
I need some help with routing and failover

Ether 1 WAN = Static ip lets say 111.111.111.111
Ether 2 WAN = Dhcp client lets say 222.222.222.222

Ether 5 LAN = LAN 192.168.0.0/24
Ether 6 LAN = LAN 172.16.0.0/21

The scenario=

Ether 1 would be the internet access to Ether 6
Ether 2 would be the internet access to Ether 5
Ether 5 and Ether 6 should not be able to talk to each other(i think it would be something like ip>firewall>filter,src address list Ether 5,dst address list Ether 6,action=drop.And Vice versa)

At normal condition the route would be
Ether 1 WAN Online -------------------- Ether 6 LAN 172.16.0.0/21

Ether 2 WAN Online -------------------- Ether 5 = LAN 192.168.0.0/24

At the event of any one of two WAN failure,the WAN that still online then would take over the offline WAN traffic.
Something like this =

Ether 1 WAN Offline -------------------- Ether 6 = LAN 172.16.0.0/21.

failover =

Ether 2 WAN Online -------------------- Ether 5 = LAN 192.168.0.0/24
|
|
-------------------- Ether 6 = LAN 172.16.0.0/21.

and vice versa =

Ether 2 WAN Offline -------------------- Ether 5 = LAN 192.168.0.0/24

failover =

Ether 1 WAN Online -------------------- Ether 6 = LAN 172.16.0.0/21
|
|
-------------------- Ether 5 = LAN 192.168.0.0/24

Remind you that Ether 2 WAN is a dhcp client,every now and then it would get renewed,may or may not with the same ip as it was.
Any idea?

By the way,this is offtopic,but ill ask anyway.
Ether 6 LAN 172.16.0.0/21 run a dhcp server on its interface,pool is 172.16.0.30 to 172.16.7.250.But when i checked at dhcp server > lease,only 172.16.7.xxx is offered to the client.
the address from 172.16.0.30 to 172.16.6.254 doesnt seems to be offered to the client device.Why?
Anything i should know about classless subnet implementation on mikrotik?