@Jim-69 

Hello, 

"DHCP address reservation" or "IP Reservation" specifically means that the router will always offer the given address whenever the host asks for one using the DHCP auto-configuration protocol. However, only DHCP offers were made static, but the router's IP-MAC neighbor cache (aka the ARP cache) is still filled in dynamically using ARP. Meaning, if you bypass DHCP and manually configure another host to use the reserved address, it'll work. As soon as the "IP-old MAC" cache entry expires, the router sends a new ARP query, learns the new MAC address, adds "IP-new MAC" to the ARP cache, and packets go to the 'new' host.

"IP-MAC binding" or "ARP Binding" won't necessarily affect DHCP, but it does add a fixed IP-MAC entry to the router's neighbor cache. If another host tries to use the same IP address, the router won't know that. It will trust the fixed IP-MAC binding, and will always send packets to the "bound" MAC address, even if the host is actually offline.

So far, IP-MAC binding primarily sounds like a security feature, it partially avoids "ARP spoofing" attacks, and works even if DHCP is turned off entirely.

Hope this helps.