Depending on how your network topology is set up.
If its a flat network, I assume you have a network setup to hold over 700 IP addresses such as a class B network, then the MX's DHCP will give out addresses within that subnet. All you have to do is turn on DHCP for that VLAN holding the 700 computers.
If you're using /24 subnet, then you can only have 253 addresses (one is the MX and the other two unusable by hosts). If your network is flat, then you probably need a /22 which hold 1022 hosts.
However, you might want to consider creating VLANs to better manage those 700 computers in an organized way. You can have a DHCP server for each VLAN on the MX.
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