Expanding DHCP-range

Hi,

I need to expand the IP-range on our LAN handling user devices and I would like some input if I'm on the right track here. Currently the IP-range is 192.168.40.0/24.

I was thinking that I could change the netmask to 192.168.40.0/23 in our router which would give me the IP-range of 192.168.40.1 to 192.168.41.254 and then change the DHCP-scope to reflect this.

As I understand there is nothing else I need to do, is that correct? We are running 10 VLANs but that should not matter in this case. There are some communications between some of the VLANs but since firewall policies are based on VLAN and individual IP-addresses it should work without reconfigure.

Since I don't want any disturbances, what do you think of the actual change? Could I change the router to 192.168.40.0/23 and then over a couple of days change the servers to the new netmask and then finally change the DHCP-scope. Or will communication be lost once I make the change in the router.

E.g. will 192.168.40.1 255.255.254.0 be able to communicate with 192.168.40.20 255.255.255.0 ?

Of course 192.168.40.1 255.255.255.0 would not be able to reach 192.168.41.30 255.255.254.0

Also, this is not the case, but how would you expand/add to the IP-range if subnets 192.168.39.0/24 and 192.168.41.0/24 were already assigned on other VLANs?

Thanks for any reply and have a nice weekend.