From the Rslogix help files:
This feature is available when using SLC 5/05 OS501 and later processors.
The Channel to channel pass-thru feature lets you pass data from the processor's serial port (channel 0) to its Ethernet port (channel 1) and vice versa. The serial port must be configured for DF1 point-to-point or DH-485 communication.
Setting up pass-thru communications
Make sure the following conditions are met:
The serial port (channel 0) must be configured for DF1 point-to-point or DH-485 communication. Select your driver on the Channel 0 - System Mode screen.
A routing table file must be created. This places a routing table icon in the project tree. Select an integer file for the routing table on the Channel Configuration - Chan 1/System screen. This file stores up to 128 internet protocol (IP) addresses that may be accessed by a device or devices connected to the RS232 serial port using either the DF1 point-to-point or DH-485 protocol. Within this table the 4-byte dotted decimal IP address required by Ethernet protocol is cross referenced to a single-byte address making it compatible with the DF1 and DH-485 protocols.
The integer file containing the routing table must be at least 2 elements long.
You must enter the internet protocol (IP) addresses into the routing table. Do this by accessing the routing table from the project tree and typing in the IP addresses that may be accessed by devices connected to the RS232 serial port. You can store up to 128 IP addresses here. Each IP address requires 2 words of the integer file. If an Ethernet device's IP address is not in the routing table you cannot send data packets through to the RS232 serial port side. The routing table is stored in the SLC 5/05.
Two bits in the Channel 1 - status file must be set or reset to control whether the gateway feature is enabled for your communication requirements.
If you are using DF1 point-to-point communication, make sure bits S:34/0 (DH-485 Gateway Disable Bit) and S:34/5 (DF1 Gateway Enable Bit) are set to 1.
If you are using DH-485 communication, make sure bits S:34/0 (DH-485 Gateway Disable Bit) and S:34/5 (DF1 Gateway Enable Bit) are reset to 0. This is the default condition for the software.
Warning! Take care when downloading a new user program to a functioning 5/05 gateway link. After a download the 5/05 processor immediately begins using the new program. To avoid disruption of the gateway operation or alteration of the communication link, be sure that the routing table contents, the enable bit, and the link IDs in the new user program are identical to those of the previous user program.
RSLogix 500 - Copyright Rockwell Software 2000, 2001, 2002