Figure is a diagram showing the four types of memory in the router. RAM holds running IOS as well as many processes that the IOS starts including routing table, ARP table, running configuration, and packet buffer. NVRAM stores the startup-config file. Flash stores the IOS files. ROM stores POST and the ROM monitor firmware, which is a limited IOS. The figure has two buttons, one for RAM and one for ROM. Clicking the buttons provides more information.