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Local Name Table Name Assignment

The second aspect involves building a name table that contains a mapping of symbolic names to associated IP addresses. A name assigned in this table is also known as an alias. A network address name assigned in the local name table can be resolved by Local Name Table Name Resolution, as described in a following section. This table may be created as follows:

ƒFor the Series 90-70 Ethernet Interface (Type 2) and Series 90-30 CPU364, a name table can only be created using the Windows-based PLC programming software (if supported). For more information, refer to the chapter: “Ethernet Global Data”.

ƒFor the Series 90-30 Ethernet Interface, a name table can only be added, edited, and deleted with the Station Manager command, CHNAMETBL. This command is documented in GFK-1186, TCP/IP Ethernet Communications for the Series 90 PLC Station Manager Manual.

DNS Name Assignment

The third aspect involves connecting and configuring a DNS (Domain Name System) name server to the network. This DNS name server contains a database of name assignments and the corresponding address information (IP address) for each of these names. This DNS name server can be queried to acquire the IP address of a symbolic name known to that DNS name server. A network address name assigned in a DNS name server can be resolved using DNS Name Resolution, as described in a following section. Please ask your network administrator for more information about the availability of a DNS name server on your network.

Name Resolution

Name resolution involves resolving a symbolic name (network address name) to its necessary address information required for communication. Without name resolution functionality, a user is required to know this addressing information (that is, IP address) to establish communication with a remote device. Name resolution provides users a means to also use a symbolic name to reach the remote destination.

For the purposes of this description, the client is the device which needs to resolve a symbolic name. This symbolic name represents the IP address of the server. Possible clients include a user of the Host Communications Drivers and users of the client capability on the Ethernet Interface (for example, Channel API). Possible servers include the Ethernet Interface (for example, SRTP Server) and the Host Communications Drivers (for example, unsolicited messages).

Name resolution of a symbolic name into an IP address follows a strict precedence rule as follows: (The precedence order is configurable as an advanced parameter using the Station Manager.)

1.Local Name Table

2.DDP

3.DNS

Each of these is described in more detail in the following sections.

Local Name Table Name Resolution

Local name table name resolution involves a simple table lookup to see if a mapping of the symbolic name to its IP address information exists. Configuration of this table is described in the topic “Local Name Table Name Assignment” earlier in this chapter.

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TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002

GFK-1541B

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GE GFK-1541B manual Name Resolution, Local Name Table Name Assignment