Most of the time in a small network, we will be using the Layer 3 device as a default gateway and a DHCP server. And most of the time also, we will be excluding the gateway’s ip address from the dhcp pool. Just to save 1 more configuration line and for the sake of knowledge, the IP address configured on the router interface is automatically excluded from the DHCP address pool :). You need to exclude addresses from the pool if the DHCP server should not allocate those IP addresses.
