Dhcp – Echelon IP-852 Channel User Manual

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

Note: The diagnostic information provided about the IP-852 devices (indicated by the

varying IP-852 device icon colors) is more complete than the diagnostics provided by the

changing colors of the NAT gateways. The IP-852 Configuration Server cannot acquire

the same level of diagnostic information about an NAT gateway as it can about IP-852

devices. See Table 2.1 for the descriptions of the different IP-852 Configuration Server
icon colors.
The IP-852 Configuration Server acts as a relay station for all information pertaining to

channel members, including which L

ORKS

subnets are on the far side of which IP

address.
Whenever a L

ORKS

routing table changes (this can happen while making a network

variable connection) or a new member is added to the IP-852 channel, the IP-852

Configuration Server relays this information to all devices on the channel that need to

know.
Once all channel devices have been inaugurated into the IP-852 channel, and all

ORKS

device installations and connections have been made, you can shut down the

IP-852 Configuration Server software (you can leave it running, however, to ensure it is

available as required for future configuration changes).

DHCP

For small networks, manually configuring the IP address of each device on the network

is fairly simple. However, as the number of computers on your network grows, assigning

each computer on the network its own IP address can be cumbersome. To solve this

problem, a system called Dynamic Host Configuration Protocol (DHCP) was created to

automatically assign network computers an IP address. Most computers use DHCP.
With DHCP, computers broadcast a message on the local network asking the DHCP

server to assign them an address, instead of using a pre-defined address. The DHCP

server stores a list of the assigned addresses and makes sure that no two requestors are

given the same address. This greatly simplifies the job of the network administrator, but

in the case of Web servers (or IP-852 devices), can create some difficulties.
The DHCP server resides on the network and assigns IP addresses. When you enable
the Automatically Obtain IP Address property in the configuration Web pages for a

SmartServer or i.LON device (i.LON

100 e3 Plus Internet Server or i.LON 600 IP-852

Router), you are asking Windows to get its IP address from a local DHCP server. DHCP

is commonly used for workstations, but seldom used for Internet-accessible servers. For

example, your company’s Web server likely has a static IP address instead of a DHCP

assigned address.
DHCP addresses are assigned in the order computers are powered on. Computer 1 may

be assigned address 100, computer 2 may be assigned address 101, computer 3 may be

assigned address 102, and so on. If computers are powered down and then later

restarted, there is no guarantee that they will receive the same address. This is a

problem if you want to setup a communication channel between a set of computers, as is

done when creating an IP-852 channel. In an IP-852 channel, each device knows the

addresses of other devices on the network. If those addresses change because a peer was

power cycled, then all members of the group need to be updated with the new IP address.

This is easily accomplished by updating an entry in the IP-852 Configuration Server, but
the process is manual, which makes it impractical for larger networks. To prevent
configuration problems due to changing IP address, assign static IP addresses
to all the IP-852 devices on an IP-852 channel.