One can upgrade the memory of a Cisco router by purchasing the correct part to do so and doing it oneself. This solution is not recommended to those who do not feel technically competent with regards to the inside of a computer. Another option would be to buy the part and have a computer geek do the upgrade for one.
Cisco router memory has over 120 gigabytes. That is a lot of memory for a router. This item can be found on either eBay or Amazon for a very cheap price.
Inside the router's chassis.
There are three major parts of the router that can be upgraded:DRAM memory, Flash Memory, and the IOS operating system that runs on it.DRAM and Flash can each be a maximum of 16 MB (try ebaying for cisco 2500 flash or memory), and IOS images can be downloaded from Cisco if you have a valid Cisco service contract.
Ram
Flash Memory
config tftp run
In a Cisco router, the memory that stores packet buffers and routing tables is known as Dynamic Random Access Memory (DRAM). DRAM is used for storing the operational data of the router, including routing information and temporary packet data during processing. In contrast, the router's startup configuration is stored in Non-Volatile Random Access Memory (NVRAM).
whenever you log into your cisco router....
The Security device manager is stored in the Router's Flash Memory
The startup configuration file on a Cisco router contains the configuration settings that are loaded into the router's memory when it boots up. It specifies parameters such as interface settings, routing protocols, access control lists, and other operational settings required for the router to function properly. This file is stored in the router's non-volatile memory (NVRAM), ensuring that the configuration persists even when the router is powered off. Essentially, it serves as the baseline configuration that the router uses to establish its operational state.
Some recommended books about Cisco routers are: Cisco Router Configuration, Cisco Routers For The Desperate, Cisco Routers for IP Router, Cisco CCNA Routing and Switching.
TFTP server, Flash