When it comes to managing IP addresses, few of us would forget to track the IPs we assign manually to our WAN interfaces, servers, switches, and etc. However, once we decide to assign a DHCP scope to a subnet we tend to "set it and forget it". In many cases, this is a big mistake. For those of us that have been around awhile, we can remember situations where DHCP wasn't available and we had to assign all of our users' IP addresses by hand. Wow did that suck. I remember having to have multiple IP address tracking spreadsheets in Excel because I had too many addresses...