Data rate cannot be set in DumbbellNetwork template network

[adamgeorge309]

In DumbbellNetwork (inet/networks/ethernet/DumbbellNetwork.ned), the network nodes are connected with EthernetLink connections, and a default Ethernet bitrate is set on the interfaces. However, Ethernet MAC module gets the bitrate from the channel. This leads to the following error:

Invalid ethernet transmission rate 0 bps -- in module (inet::EthernetMac) Congestion.client1.eth[0].mac (id=69), during network initialization