Published: 2003 October


How do I determine if I have the right amount of memory and flash for a Cisco software image?

Read the explaination at "How to Choose a Cisco IOS® Software Release" on

Is it just me, or is this pretty convoluted? In fact, it's just dumb. The current line doesn't even
tell what kind of "memory" it is...


October 17, 2003


While attempting to document the changes to the 'show version'
command, I came across another aspect that desperately needs improvement.

According to the document on "How to Choose a Cisco IOS® Software Release"
[ ]
we make customers go through a convoluted process of using "show version" to figure
out how much DRAM they have to see if they can use a particular software image.
(specifically, "if you have this platform, use this value, but if you have
this platform, add these two values together...", and not all platforms are listed).

But the "IOS Upgrade Planner" (and similar documents) lists the requirements
very simply for an image:
Minimum Memory = x MB
Minimum Flash = y MB.

View from Upgrade Planner:

Couldn't we push for a simple command across platforms that just shows
installed DRAM and installed Flash, so that customers know if they can
download a desired image?
(Note that the current "show memory" command is not at all helpful
in this respect.)

["show memory" processor > Total(b) is the total amount of memory, in bytes, available for the processor after the Cisco IOS software is loaded. view details ]

Something like:
Router# show memory basics
DRAM : 64 MB
Flash: 16 MB
Packet Memory: 8,192 KB (shared)
(or include that simplified data in the 'show version' command)

Instead of the current:
Router# show version
. . .
Cisco 3660 (R527x) processor (revision 1.0) with 57344K/8192K bytes of memory.
. . .
16384K bytes of processor board System flash (Read/Write)
. . .
(it is not simple to determine from the above that I have
the minimum 64 MB needed to run my software image)

I think this is a customer satisfaction issue.

Thank you for considering this,

"Some routers (for example, 2600, 3600, and 4000 Series) require a minimum amount of I/O memory to support certain interface processors.
If the router is running low on shared memory, even after a reload, physically removing interfaces solves the problem."

Understanding the Cisco IOS


Show version "processor" Line:

This line DOESN'T tell you (as you might suspect) memory used and free memory.....

This line can be used to determine how much Dynamic RAM (DRAM) is installed on your system, in order to determine if you meet the “Min. Memory” requirement for a software image. DRAM (including SDRAM) is used for system processing memory and for packet memory.

Two values, separated by a slash, are given for DRAM:
The first value tells you how DRAM is available for system processing, and the second value tells you how much DRAM is being used for Packet memory.

The first value, Main Processor Memory, is either:
- The amount of DRAM available for the processor, or
- The total amount of DRAM installed on the system.

The second value, Packet Memory, is either:
- The total physical input/output (I/O) memory (or “Fast memory”) installed on the router (Cisco 4000, 4500, 4700, and 7500 series), or
- The amount of “Shared memory” used for packet buffering. In the shared memory scheme (Cisco 2500, 2600, 3600, and 7200 Series), a percentage of DRAM is used for packet buffering by the router's network interfaces.

NOTE: The terms “I/O Memory” or “iomem”; “shared memory”; “Fast Memory” and “PCI memory” all refer to “Packet Memory”. Packet Memory is either a seperate physical RAM stick/module (?), or shared DRAM.

(goto)# Cisco IOS Software Versions
(goto)# Cisco IOS Features