What this CP 343-1 Advanced does that a basic Ethernet module won't
The 6GK7343-1EX21-0XE0 is a CP 343-1 Advanced communications processor that fits a double-width slot in an S7-300 rack. It gives the PLC a PROFINET interface with DCP (Discovery and Configuration Protocol) support, so you can assign device names and IP addresses over the network without needing a memory card or MPI cable — a real time-saver when commissioning a line of identical stations. It also carries NTP (Network Time Protocol) for synchronizing the PLC clock across the plant network, which matters when you're correlating time-stamped alarms from multiple CPUs or drives.
The first (and only) interface runs at 10 or 100 Mbit/s, auto-negotiating to match the switch port — no manual speed setting needed. That's the standard for PROFINET RT and most plant-floor Ethernet traffic. It supports up to 16 multicast stations, which is the ceiling for distributing time-sync or diagnostic telegrams to a group of devices. If your application needs to broadcast to more than 16 receivers simultaneously, you'll need to segment the network or use a different CP variant. TCP/IP is supported natively, so the module can handle Modbus TCP, FTP, or custom socket connections from the S7-300 user program without an additional gateway.
Power, mounting, and environmental fit
The module draws power from the S7-300 backplane (5 V) and also needs an external 24 V DC supply via the 2-pole pluggable terminal block on the front. Total power loss is 5.8 W — that's the heat it dumps into the enclosure, so factor it into your panel cooling calculation if the cabinet is tight. Physical dimensions are 80 mm wide, 125 mm high, and 120 mm deep — it takes up two standard S7-300 slot widths. Mounting is on the standard S7-300 DIN rail; the module snaps on and locks with the same mechanism as the CPU and I/O modules. Rated IP20, so it belongs inside a cabinet with the door closed.
Configuration tools and removable storage
Configuring the CP requires STEP 7 V5.3 SP3 or higher — older versions won't recognize the module in the hardware catalog. The configuration (IP parameters, device name, filter rules) can be stored on a C-PLUG removable storage medium, which lets you swap a failed CP and have it pick up the same settings without re-downloading from the engineering station. It supports SNMP v1 for basic network management visibility, and IP-based ACL (Access Control List) to restrict which devices can communicate with the PLC — a first layer of defense against unauthorized access on the plant network.