Echelon IP-852 Channel User Manual

Page 48

Using NAT, DHCP, DNS on an IP-852 Channel

DNS

DNS is a mechanism that translates an IP host name like www.echelon.com into a

numeric IP address like 205.229.51.8. For example, when you enter www.echelon.com in

your Web browser, your Web browser queries a DNS server to find the IP address. It

then requests the home page from the numeric IP address—not the IP host name.

Because the process is transparent, many people are not aware of the existence of

numeric IP addresses.
IP host names are usually used to reference servers such as a Web server

(www.echelon.com), a database server, or a file server. Because these servers are fixed

assets, they are usually assigned a static IP address. That static IP address is also

entered into a DNS server so that the mapping between the IP host name and the

numeric IP address can be made.
If you are in control of your local DNS server, you should give all participants in your

IP-852 channel static IP addresses and create DNS entries for each participant. This

allows you to specify IP host names when setting up the IP-852 channel in the IP-852

Configuration Server, instead of numeric IP addresses. The IP-852 Configuration Server

will translate the IP host name into a numeric IP address and pass that address to all

members of the channel.

For example, if you had a static IP address at your local network, you could register that

IP address with one of the Internet registrars (such as register.com) and associate a

name with that static IP address. The registrar will propagate the address/name pair

throughout the Internet’s DNS servers for you, ultimately allowing you to tell people to

Note: When a browser tries to view a Web site, it asks the DNS server to translate the

name of a Web site into an IP address. It then uses the IP address to contact the Web

site. The actual IP packets never contain the proper name of the Web site, only the hard

IP address that was resolved by the DNS server. In addition, the IP-852 devices

themselves do not query DNS servers to resolve addresses; they only work with numeric

IP addresses provided by the IP-852 Configuration Server.
This only works for static IP addresses because each time you change the IP address, you

need to contact the registrar to setup the new address/name pair across the Internet.

This may take up to two days for an address/name pair to propagate through the entire

Internet.
To set the Echelon IP-852 Configuration Server automatic IP host name address

translation, follow these steps:

1. In the IP-852 Configuration Server, click Network, click Settings, and then click

the IP Host Names tab.