A shared network is a network segment to which you assign two or more subnets. You can combine individual contiguous networks into a shared network to allow the DHCP server to assign IP addresses from any subnet (that resides on the same network interface) in the shared network.
If I configure it like this, I can see that it always give ip address from the first range. Does the server give ip address either from the two range?
Also, without shared network configured, I can see the same behaviour and I think it is by design (without shared network)?
I step back. I think my sample is incorrect. It is not leveraging the shared network.
I configured secondary address in my cisco router
ip address 184.108.40.206 255.255.255.0
ip address 220.127.116.11 255.255.255.0 secondary
and once the 1st subnet ran out of address, it switched to the secondary subnet. These two subnets are in the shared network.