One of the problems network administrators face today is the fact that Dynamic Host Configuration Protocol (DHCP) is inherently a dynamic protocol, while the Domain Name System (DNS) is static. DHCP has made distributing the IP addresses much easier than manual assignment, but the flexibility provided by such a dynamic protocol is countered by the need to manually alter the text files associated with the DNS database. If only the two server processes could communicate!
Given the desire for more centralization and automation in maintaining the IP address and domain name space, many vendors have been investigating the possible solutions.
A typical client/server mechanism for Dynamic DNS (DDNS) is shown in the visual with Client A.
- A-1: The client sends a typical DHCP request to the DHCP server.
- A-2: The DHCP server determines an appropriate IP address for the client and makes an offer in the standard DHCP fashion (for simplicity, the visual does not show the usual 4 packet exchange).
- A-3: Once the client has received its IP address assignment, the DHCP server then sends an update to the DDNS server, indicating the address used and possibly the client’s name (e.g., a NetBIOS name).
Another possibility in synchronizing the DHCP and DNS databases is illustrated in the exchange between Client B and the server.
- B-1: The client sends a typical DHCP request to the DHCP server.
- B-2: After determining an appropriate IP address for the client, the DHCP server then queries the DDNS server to find a name associated with the chosen IP address.
- B-3: The DDNS server returns the name found in the DNS database.
- B-4: The DHCP server responds to the client with an IP address and a valid client name.
In either case, the DHCP and DDNS server processes have up-to-date information regarding the name and IP address assignments. Adding a dynamic protocol into the mix guarantees that no stale information will exist in either database, and further simplifies IP network administration.