We are sending UC RDMA transfers over InfiniBand between blade servers with Mellanox HCAs and some custom hardware. The custom hardware sometimes receives packets that are flagged as having an invalid opcode. The opcode has the value 0x80, which is a reserved, undefined value. The packet has a single 32-bit word payload and it is sent with the normal destination QP that other traffic uses with no problem. Have anyone heard of this kind of problem?