Integrated routing and bridging (IRB) is a feature that allows you to route between different bridge groups on a Cisco FTD device. A bridge group is a logical interface that acts as a container for one or more physical or logical interfaces that belong to the same layer 2 broadcast domain. You can assign an IP address to a bridge group interface (BVI) and enable routing protocols on it, just like a regular routed interface. However, when you run a dynamic routing protocol on a Cisco FTD device in IRB mode, you can only use nonbridge interfaces as routing peers. You cannot use bridge group interfaces or bridge group member interfaces as routing peers2. This is because the routing protocol packets are sent and received on the nonbridge interfaces, and the bridge group interfaces are used only for forwarding data traffic3.