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Industrial Ethernet S7-300/400 CPs -- Setting up and parameterizing hardware -- Initializing and parameterizing modules
Why is there no entry with the current firmware version for my module in the STEP 7 hardware catalog?
What should you watch out for when a MAC address is entered for the PROFINET interface or GBIT interface in the configuration of the Industrial Ethernet CP343-1/CP443-1?
How do you configure a shared device when you are using a CPx43-1 Advanced as PROFINET IO controller and the GBIT interface of the module is networked?
Which "local_device_id" do you parameterize in order to establish a connection to FB65 "TCON" for open communication via Industrial Ethernet?
Which Industrial Ethernet CPs support the DHCP Option 12 (Host Name) and how do you configure the DHCP Option 12?
What should you watch out for when parameterizing the watchdog time when a ring redundancy is established with the Media Redundancy Protocol?
How do you use an Industrial Ethernet CP or SCALANCE S as a gateway?
How do you disable the "Link Layer Discovery Protocol" function at the ports of an IE CP of S7-300 or S7-400?
Where can you find sample S7 programs and documentation for communication via gateways and network components, and for security in networks on the SIMATIC NET Quick Start Collection?
What should you watch out for when operating a CP443-1EX20 V2.0 on a CPU V5.1?
Changing the configuration data of users for CP 343-1 IT and CP 443-1 IT
Loading the configuration via LAN into the IE-CP in "STOP" mode
Special points when setting the LAN medium for Industrial Ethernet CPs
Starting up automation systems with Industrial Ethernet without previous node initiation via MPI
Rejected diagnostics connection via TCP/IP protocol after changing the MAC address
Establishing an online connection to an S7-300/S7-400 CPU through several Ethernet interfaces
What should you pay attention to when formatting the file system in the S7-300 and S7-400 Industrial Ethernet CPs?
What should you watch out for when replacing the CP443-1 (6GK7443-1EX11-0XE0) with a CP443-1 (6GK7443-1EX20-0XE0 V1.0) in STEP 7 V5.4 SP3?
What is the meaning of the configuration option "Activate Web server" with CP443-1 EX20?
Why with CP443-1 Advanced is a different firmware version than the module displayed in the C-PLUG info text in the NCM S7 Diagnostics?
Which options are available for assigning the PROFINET IO controller a new IP address?
How can you configure an S7 CP during runtime?
How do you disable the S7 routing functions?
Which manufacturer ID, in other words OUI (Organizationally Unique Identifier), does SIEMENS AG use for the MAC addresses of network-compatible devices?
How can you protect the S7-300/400 against unauthorized access from the LAN (local area network)?
What should you watch out for when using the function block FB55 "IP_CONFIG" to configure an Industrial Ethernet CP?
Why are some of the newer versions of the names of SIMATIC NET modules not used in the hardware catalog?
Why can't my SIMATIC S7-300 Ethernet CP run as many S7 communication connections as specified?
How does connection multiplexing work and how do you configure it for SIMATIC S7-300 Ethernet CPs?
How does connection multiplexing work and how do you configure it for SIMATIC S7-300 Ethernet CPs?
Part number:

Connection multiplexing means that all S7, PG and OP connections, which run through the CP, are switched to a multiplex connection between the CP and the CPU. This means that the CP always reserves one connection resource in the CPU. The reservation of an S7 connection resource in the CPU for multiplex operation is independent of whether an S7 connection is configured. No other connection resource in the CPU is reserved by any of the other bilateral S7 connections that you configure. Another characteristic is that the communication speed diminishes with every connection configured. The advantage is that with multiplexing you can configure more connections than you can without.

Fig. 01 shows that a total of seven S7 connections have been configured, but only two connection resources are reserved in the CPU.

Fig. 01

The following Ethernet CPs support connection multiplexing.
Name Order number
CP343-1 6GK7343-1EX11-0XE0
CP343-1 6GK7343-1EX20-0XE0
CP343-1 6GK7343-1EX21-0XE0
CP343-1 6GK7343-1EX30-0XE0
CP343-1 IT 6GK7343-1GX11-0XE0
CP343-1 IT 6GK7343-1GX20-0XE0
CP343-1 Advanced 6GK7343-1GX21-0XE0
CP343-1 Advanced 6GK7343-1GX30-0XE0
CP343-1 Advanced 6GK7343-1GX31-0XE0
Table 01

Proceed on the basis of the following instructions to activate connection multiplexing in your CP.
No. Procedure
1 Open the CP's object properties in the hardware configuration.
2 Open the "Options" tab.
3 Enable the "Reserve CPU connection resources" option.

Fig. 02

4 Save and compile the hardware configuration.
5 Load the configuration into the CPU.
Table 02


  • Connection multiplexing only works for fully specified bilateral S7 connections.
  • As soon as connection multiplexing is enabled, a CPU connection resource is reserved, even if a connection has not yet been configured.
  • A separate connection resource is reserved in the CPU for each unilateral S7 connection.
  • The multiplex connections and the unspecified S7 connections do not appear in the CPU's Properties dialog ("Communication" tab), although they still count. When communication services log on (which means that the connection is set up), the CPU connection resources are reserved in chronological order.

You have a CPU that can handle a maximum of 32 connections. Taking away the connections for PG/OP communication, that leaves 30 connections for the S7 communication (value for S7 basic communication has been set to 0).

Fig. 03

You configure one or more bilateral S7 connections to other devices.

Fig. 04

These connections run through the multiplexing, which means that only one connection resource is reserved in the CPU. However, this does not appear in the Properties dialog.

Fig. 05

 Entry ID:22276762   Date:2013-11-22 
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