Cisco 4400 Series Routers (4451-X and 4431) ship with a default memory of 2 GB of DRAM for the data plane, 4 GB of DRAM for the control plane, and 8 GB of flash memory. The 4-GB DRAM configuration for the control plane is derived by the installation of two symmetrical dual in-line memory modules (DIMMs) of 2 GB in each of the memory slots. When upgrading memory to higher densities, both memory slots must be populated with DIMMs of the same type and density for high system performance.The Cisco 4000 Series platform does not support the use of different DRAM densities in the two available DIMM slots or the use of only one slot.