The Cisco Management Information Base (MIB)

The Cisco Management Information Base (MIB) is an operating system component that’s included with every recent IOS distribution. Network administrators are able to manage and view device memory over the network Applications that deal with Cisco memory management have MIB as a crictical software prerequisite, and it’s used to report data to RME (Resource Manager Essentials) when other software is being installed onto a particular Cisco device.

Cisco devices all have several types of memory; processor memory, or RAM memory, Cisco flash memory cards, PCI memory, and shared memory which is also known as I/O memory. Not all Cisco memory will be evenly distributed depending on the device – some devices will have more processor memory, some more PCI, etc. There is a table in the MIB database which contains a number of entires, each linked with two variables, and each entry is meant to correspond with part of the pool of memory. The two MIB variables are ciscoMemoryPoolFree and ciscoMemoryPoolUsed. For ever pool, each is the complement of the other, and no matter what, adding them together will give the size of any pool of Cisco memory when given by RME. Then, all the totals can be added and the total amount of I/O memory can be determined.

If the software is an obsolete version of the IOS, only the size of processor memory can be reported and therefore don’t have more advanced bits. All versions of the Cisco Internetwork Operating System after version 11.1, which is used by the majority of Cisco routers and hardware (besides firewalls) can report MIB values over a network by using SNMP. This allows network administrators to query the database across the network regardless.

On all Cisco IOS devices, the Cisco Inventory application refers to the MIB when a device is imported into inventory. The Software Image Manager (SWIM) does this as well when it needs to verify that there’s enough shared memory available for all software images during upgrading.

There can be discrepancies between the methods by which different applications determine how much memory is available. This is because of how much IOS has changed along with Cisco. Individula applications have kept their legacy support even after upgrading, so Cisco recommends to customers to use the information that’s give by the Inventory program’s Detailed Device Report. This will be more accurate in determining memory. For those users with pre 11.1 versions of IOS, the output from the Show Version command would serve this purpose better.