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DHCP and Dynamic DNSThis page is has been moved to the new SoC Document Repository. The new URL for this page is: https://docs.comp.nus.edu.sg/node/1718 SoC network has moved toward full-scale deployment of DHCP for IP assignment and network configuration for most computers (or other networked devices) in the network. There is often much user resistance to this move. One of the main reason behind this is the perceived lack of a "well-known address" for hosts configured via DHCP, particularly those who intend to provide public Internet service. The purpose of this document is to dispel this misconception and to introduce the concept of Dynamic DNS. Perceived Lack of Well-Known AddressDHCP clients are assigned IP addresses from a DHCP server. Although the DHCP server does try to reassign the same IP address to a client that it previously had, this cannot be guarranteed and as a result, the client's IP address will sometimes change. Users perceive this lack of a fixed IP address as a problem because their computer cannot be reached via a "fixed Internet location". However, since most Internet users do not memorize IP addresses, this perceived problem is not a real issue. For example, it is unlikely that you remember the Yahoo! website by its IP address. DHCP clients do continue to be reachable via a fixed fully-qualified domain name, the host name component of which is actually that of the registered owner's choosing. This is really the issue that is important. The Yahoo! website is more popularly known by the URL www.yahoo.com, not by its IP address! Dynamic DNSIn a Dynamic DNS (DDNS), the zone entries can be dynamically updated in realtime by a DDNS client. This means, for example, that the hostname records in a DNS can be updated by a DHCP server (which also functions as a DDNS client). Dynamic DNS is deployed in SoC network. As a result, the use of Dynamic DNS does in fact continue to provide DHCP-configured hosts with a well-known and fixed fully-qualified domain name. The hostname component of the client is specified in the host registration (i.e., choosen by the registered owner). The DDNS domain name used in SoC is ddns.comp.nus.edu.sg. DHCP clients will have their hostnames updated to this domain according to information supplied by the DHCP server. For example, if there is a DHCP client with the registered name host1, then when it is booted up and assigned an IP by a DHCP server, the fully-qualified domain name host1.ddns.comp.nus.edu.sg will be added to the Dynamic DNS and the name will point to the client's assigned IP address. Personal DNS at MySoC.NetMySoC.Net also provides a free Personal DNS service similar to the dynamic DNS service mentioned here. More information is available at Personal DNS.
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