Types Of Memory On A Cisco Device

Cisco provides products and services to help in building computer networks, including switches, routers, and software at individual and business scales. All the networking hardware, operating systems, and routers use different types of memory and it is determined by what functions the memory serves in the system. For example, a router ensures a secure path for the successful delivery of data transmission. Router uses a routing table where static and dynamic addresses are allocated which helps in successful transmission. These addresses are stored in memory. For easy and effective handling of data and information, memory is categorized into different types.

The types of memory on a Cisco device

  • RAM (DRAM)

  • Flash Memory

  • ROM


Let’s explore the article by step by step explanation of types of memory required on a cisco device.

1.RAM (Dynamic Random Access Memory)

The memory used by Cisco devices uses DRAM which is Dynamic Random Access Memory, it is the same as that RAM. It has a volatile nature. It loses its power when the system is shut down immediately if any one device crashes. It is designed to work with computer systems that have certain device requirements. One requirement would be the function that the memory performs. Whenever we restart a router, the previous data gets deleted. Information stored in RAM is temporarily stored in a router.

In a cisco router, RAM is used for running Cisco operating systems and buffers. RAM can also be used to store routing tables, keeping cache and certain packet buffering. Also, RAM holds the configuration of the router that we use which means if any changes that we make in configuration, that are saved in RAM until we save them in NVRAM.

RAM can be divided into two categories

  • First is the main processor memory which stores the details about configuration of the router, ARP and tables. It also stores important data that is used regularly, like the configuration settings that are currently in use and any routing tables.

  • Second is I/O memory which is a type of secondary storage memory that saves the data packets.

2. Flash Memory

Flash memory is a type of non-volatile memory, it removes the data in blocks and rewrites data at byte level. It is also called Erasable Programmable Read Only Memory (EPROM). We use flash memory to store and transfer data in private and business devices on a wide scale. This flash memory has the widest range of usage apart from all cisco devices available.

Benefit of flash memory is that we can get our previous data back when the router is switched off. It occupies OS Image (like internetwork OS) having this feature we can now upgrade our operating system even without removing chips. Retaining its old data is considered as the main specification of this memory. In flash memory, we are provided with multiple versions of IOS which we can restore according to our need.

3. ROM (Read Only Memory)

On Cisco devices, it is a type of memory which is usually referred to as a Boot ROM. As the name implies, it is a kind of memory which we can read only. Cisco devices start their procedure from this memory. ROM stores Power On Self Test (POST) program, it is a type of test which helps in checking whether hardware and other interfaces are working properly or not. If they are not working then POST generates an error message. After this function is performed, the bootstrap application is used for setting up the CPU of the router. It also does the task of searching and loading the operating system of the router.

ROM Monitor has a user interface which includes many options for troubleshooting failure in the chips. One advantage is that we can use IOS in this ROM to recover from major security and disasters such as loss of data in Flash random access memory. Cisco routers have chips which can be removed for their upgrade or change. It is advisable to change them after a certain amount of time for better performance of the device.

4. NVRAM (Non-volatile Random Access Memory)

It is very expensive. We store the configuration file in NVRAM. The first file that IOS will read is this startup configuration file. This memory is very fast and one great feature about it is that it also gets its data and content back when the power is down. Now we don’t have to configure the router over again after the power is down.

This memory has the ability where the data can be recovered easily even after the router is switched off. All configuration files can be saved permanently by moving these files from RAM to NVRAM. There are many more NDM projects. In terms of technology, Resistive RAM, RAM nano and RAM spin etc, they will be driving the world in future. The NVRAMs make all the commercial and financial sense which lead to bigger progress in every system.


RAM stores the task that is going on. Operating system is present in the IOS of the router in Flash memory. ROM stores the information related to POST and bootstrap programs. NVRAM where startup configuration takes place.

Updated on: 12-Apr-2023


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