Almost all advanced Cisco routers and switches are equipped with the Cisco proprietary operating systems called the IOS, depending on the version of IOS installed in your Cisco product there is an additional component called the Management Information Base (MIB) integrated into the IOS operating system. The reason why we are discussing the MIB is because, if you have a Cisco product with an IOS version greater than 11.1, chances are you have the MIB module will be available to you, and you can easily acquire accurate memory information on the product.
This of course is very useful if you plan to upgrade the memory of your product. Note: that only Cisco Pix firewalls do not come equipped with the IOS operating system. Before we go into the nitty-gritties of why you should upgrade your Cisco memory, the first thing to discuss is the types of memory that is used in a Cisco product. a) Processor Memory As the name suggests, this memory acts similar to the CPU cache in a computer, all basic computing operations of your switch, or router will depend on the processor memory, irrespective of the other memory being used, the processor memory is the first memory that is accessed and used.
All the files needed for booting and essential system files required for functioning of the Cisco product are stored in the processor memory. If you are using a product that has IOS before 11.1 then the total of all types of memory is reported as the processor memory. b) Flash Memory Card or Cisco Memory Card The flash memory is a special type of programmable memory that is used to store images of the IOS software on it, in addition the flash memory is used to upgrade versions of the router or switch being used, in fact the term 'flashing a product' means upgrading the version of IOS stored on the flash memory card.
For technically inclined people the flash memory is a type of EEPROM (Electrically Erasable PROM). c) RAM (Random Access Memory) This is often referred to as the shared memory, since the RAM is erased every time the router is restarted or when the memory is deliberately cleared, it is purely temporary in nature and is usually the easiest to upgrade. The RAM stores all data that is temporary in nature, and upgrading the RAM usually helps improve the speed and the computing power of the Cisco product. It is cheaper than Flash memory and multiple manufacturers offer RAM when compared to flash memory.
Depending on the reason for upgrading the memory, either the Flash memory or the RAM is upgraded in most Cisco products. Also high end products like routers offer multiple memory slots to upgrade both the RAM and the Flash memory if need be. The reasons for upgrading the memory of your Cisco product usually are: Increasing speed Just like conventional computes, increasing the memory of a Cisco product increases its speed. Especially if the product is a Cisco router or switch that handles large amounts of data over the network, by increasing the RAM of the product one can greatly improve not just the processing performance of the product but also improve the speed of functioning.
Improve computing capacity This aspect is best explained by taking the example of a network, let us assume we have a network that had a Cisco router and 30 computers, if the number of computers is upgraded and the same router is now supporting 100 computers, there may or may not be a change in the performance, however instead of upgrading the router to cater to the volume of data that is being sent back and forth, it is simpler to just upgrade the RAM of the router. So in a sense we are not only improving the capacity of the router, but we are also improving the product life. The same applies for routers that are interacting with other network devices, the performance of these devices also improves after a memory upgrade. But remember to use only recommended memory modules to upgrade the product's memory, as RAM for Cisco products is usually of higher quality than regular computer RAM.
John J. Stockwell is the author of this article on upgrade cisco memory. Find more information about upgrade cisco memory here.