QUESTION:
What are the settings of the DP slave interface on an S7-300 CPU so that I can route via this?

ANSWER:
If you wish to use the CPU as an I slave and this CPU is also to be an S7 router, then please note the following:

• The DP interface of the slave via which the routing is to take place must be activated. This is done in the hardware configuration. In the Properties dialog of the DP interface you must set a check mark for "Commissioning/Test operation" or for "Programming, status/modify...". Notes on this are in the enclosed table.
  
  
• The table shows the connection resources available for S7 routing connections - regardless of the other connection resources. Connection resources of the PG/OP or the S7 basis communication are not occupied.
  
  
• The following holds for CPUs 313, 314, 315 and 316:
  A routing connection resource is also occupied when a connection is to be set up via the DP interface to/from a node in the own rack (e.g. a CP 343-1). In the case of connection setup to/from a node in the own rack via the MPI interface no routing connection resources are occupied, because here the node can be reached directly.
  
  
• The following holds for CPUs 317:
  A routing connection resource is also occupied when a connection is to be set up via the DP interface or the MPI/DP interface to/from a node in the own rack (e.g. a CP 343-1).
  
  
• The following holds for CPU 318:
  The resources for routing and the other connections are managed together. More information on this is available in the reference manual "S7-300 Instruction List CPU Specifications CPUs 312 IFM to 318-2 DP", section 1.2 Connection Resources of the CPU 318-2. The reference manual is available in Entry ID : 8861817.

• It is not possible to check routing resources online.

Table 1 shows the assignment of the CPU to the different hardware configurations.

CPU order number	Number of connection resources	Fig. 1	Fig. 2	Fig. 3
6ES7 313-6CE01-0AB0	4	-	X	-
6ES7 314-6CF01-0AB0	4	-	X	-
6ES7 315-2AF03-0AB0	4	X	-	-
6ES7 315-2AF83-0AB0	4	X	-	-
6ES7 315-2AG10-0AB0	4	-	X	-
6ES7 315-6FF01-0AB0	4	-	X	-
6ES7 316-2AG00-0AB0	4	X	-	-
6ES7 317-2AJ10-0AB0	8	X	-	-
6ES7 317-2EJ10-0AB0	up to 24	-	X	-
6ES7 317-6FF00-0AB0	8	-	-	X
6ES7 318-2AJ00-0AB0	see manual	X	-	-

Table 1: CPU assignment

Routing as DP slave is not possible for Compact CPUs with firmware version 1.0.x.

Below you see how to make the setting for the DP slave in the Hardware Configuration according to the CPU used.

Fig. 1: Settings in Hardware Configuration_1

Fig. 2: Settings in Hardware Configuration_2

Fig. 3: Settings in Hardware Configuration_3