Method for message transmission in a redundant industrial communication network, in which - messages are transmitted in at least one first sub-network (101, 102) with tree topology in a way corresponding to a spanning tree protocol, wherein the spanning tree protocol is the Spanning Tree Protocol, Rapid Spanning Tree Protocol or Multiple Spanning Tree Protocol, - communication devices assigned to network nodes of the first sub-network for forming a tree topology exchange messages with topology information with one another and, on the basis of the topology information exchanged, a root network node is determined as a basic element of a tree topology by the communication devices assigned to the network nodes of the first sub-network, wherein loop-free connections are constructed from the root network node to the other network nodes of the first sub-network and the messages with topology information of the first sub-network are bridge protocol data units, - messages are transmitted in a second sub-network in a way corresponding to a parallel or ring redundancy protocol, and - the first sub-network and the second sub-network are coupled to one another by way of a plurality of communication devices, characterized in that - the parallel or ring redundancy protocol is the Parallel Redundancy Protocol, High-availability Seamless Redundancy Protocol or Media Redundancy Protocol, - for the communication devices coupling the first sub-network and the second sub-network, a first terminal group and a second terminal group are set up, wherein communication device terminals (211, 221, 222, 232) of the first terminal group are used for a message transmission in a way corresponding to the spanning tree protocol within the first sub-network, and wherein communication device terminals (212, 214, 223, 224, 231, 233) of the second terminal group are used for a message transmission in a way corresponding to the parallel or ring redundancy protocol within the second sub-network, - within a communication device coupling the first sub-network and the second sub-network, the communication device terminals of the second terminal group are connected to a communication device terminal of the first terminal group that has the lowest path costs for a communication connection to the root network node of the first sub-network among the communication device terminals of the first terminal group, - the messages with topology information of the first sub-network respectively comprise a port priority vector, which is exchanged among the communication devices assigned to network nodes of the second sub-network and adjusted. - messages are transmitted in at least one first sub-network (101, 102) with tree topology in a way corresponding to a spanning tree protocol, wherein the spanning tree protocol is the Spanning Tree Protocol, Rapid Spanning Tree Protocol or Multiple Spanning Tree Protocol, - communication devices assigned to network nodes of the first sub-network for forming a tree topology exchange messages with topology information with one another and, on the basis of the topology information exchanged, a root network node is determined as a basic element of a tree topology by the communication devices assigned to the network nodes of the first sub-network, wherein loop-free connections are constructed from the root network node to the other network nodes of the first sub-network and the messages with topology information of the first sub-network are bridge protocol data units, - messages are transmitted in a second sub-network in a way corresponding to a parallel or ring redundancy protocol, and - the first sub-network and the second sub-network are coupled to one another by way of a plurality of communication devices, - the parallel or ring redundancy protocol is the Parallel Redundancy Protocol, High-availability Seamless Redundancy Protocol or Media Redundancy Protocol, - for the communication devices coupling the first sub-network and the second sub-network, a first terminal group and a second terminal group are set up, wherein communication device terminals (211, 221, 222, 232) of the first terminal group are used for a message transmission in a way corresponding to the spanning tree protocol within the first sub-network, and wherein communication device terminals (212, 214, 223, 224, 231, 233) of the second terminal group are used for a message transmission in a way corresponding to the parallel or ring redundancy protocol within the second sub-network, - within a communication device coupling the first sub-network and the second sub-network, the communication device terminals of the second terminal group are connected to a communication device terminal of the first terminal group that has the lowest path costs for a communication connection to the root network node of the first sub-network among the communication device terminals of the first terminal group, - the messages with topology information of the first sub-network respectively comprise a port priority vector, which is exchanged among the communication devices assigned to network nodes of the second sub-network and adjusted.