The RB2011 series consists of different models. In the base model 5 * GigE + 5 * 100/10Mbps Ethernet ports are built in. Some models then add an SFP port. Some versions SFP port and 802.11b/g/n wireless. Newer versions of the models have a USB port and passive PoE on ethernet port 10 (models with “i” in the name).
Every model identifies itself to the OpenWrt linux kernel with a different model name (eg: 2011r5 for RB2011-UiAS-2HnD-IN). The OpenWrt kernel only boots when it recognizes the model name. As of Barrier Breaker, all versions of RB2011 series available by 05/2015 should be recognized.
See Mikrotik RouterBoard RB2011-UiAS-2HnD-IN for more information. The problems on that model should be the same for other models (unclear).