Trevor,
Thank you for using the SRCUG forum and posting your question. The ASA only supports DHCP reservations when connecting a client via VPN and not on the internal network. A work around could be to use your intenral switch if it supports layer 3 and manually bind the IP address to MAC address withing the DHCP Pool configuration:
ip dhcp pool {client name}
hardware-address {client MAC} ieee802
client-name {name of client}However, there is a caveat to this, you will need to create a DHCP Pool for each manual bind, you can only have one manul bind per DHCP pool.
http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-68D87544-7C6F-48C9-9DFE-56F5B7E4A89D
Configuring Manual Bindings
An address binding is a mapping between the IP address and MAC address of a client. The IP address of a client can be assigned manually by an administrator or assigned automatically from a pool by a DHCP server.
Manual bindings are IP addresses that have been manually mapped to the MAC addresses of hosts that are found in the DHCP database. Manual bindings are stored in NVRAM on the DHCP server. Manual bindings are just special address pools. There is no limit on the number of manual bindings, but you can configure only one manual binding per host pool.
Automatic bindings are IP addresses that have been automatically mapped to the MAC addresses of hosts that are found in the DHCP database. Because the bindings are stored in volatile memory on the DHCP server, binding information is lost in the event of a power failure or upon router reload for any other reason. To prevent the loss of automatic binding information in such an event, store a copy of the automatic binding information on a remote host called a DHCP database agent. The bindings are periodically written to the database agent. If the router reloads, the bindings are read back from the database agent to the DHCP database on the DHCP server.
Joshua Koch
Systems Engineer
Cisco Systems
