I've just expanded our subnet at work from /24 to /22 now that we've started running out of addresses. For ease of transition, I left all statically-assigned IPs at their original addresses and moved the DHCP pool to a new block of 254 addresses. From everything I've read and understand, it should be that simple, but instead everything broke...
The new pool works, but anything with a MAC-reserved IP either gets a generic IP from the pool, or no address at all (DHCP fails). I got desperate enough to try flushing the ARP cache and DHCP leases and rebooting the device with no effect. To make this change, all I did is edit the X2 interface to have netmask 255.255.252.0 instead of 255.255.255.0. Then added a Dynamic DHCP scope to the new block of addresses. Is there anything I could be missing? This is so broken I feel like I must've missed something big. Thanks for your help, and Happy New Year.
EDIT: Running SonicOS Enhanced 6.2.7.1-23n on TZ 500. Also, if I manually assign the addresses that DHCP should be assigning to the reserved PCs, they can communicate with other machines on the network.