show version
or
show hardware
Both commands can be used, and the output can be interpreted like the following:
Cisco Internetwork Operating System Software
IOS ™ GS Software (GS7), Experimental Version 10.2(11829) [pst 113]
System-Type (ImageName) Version Major.Minor(Release.Interim)[Who] Desc
System-Type: Type of system the software is designed to run on.
ImageName: The name of the image. This is different (slightly) for run-from-rom, run-from-flash, and run-from-ram images, and also for subset images which both were and will be more common.
Version: Text changes slightly when, for example, if given a special version of software to try out a bug fix, it will say experimental version.
Major: Major version number, which (in theory) whenever has major feature additions and changes to the softare.
Minor: Minor version number, which counts smaller but still signficant feature added.
Release: Increment of 1, 2, 3, 4… for each maintenance release of released software for every compile in some other places.
Interim: Increment on every build of the release tree in software control, which happens weekly for each release, but is only made into a generically shipping maintenance release every 7 to 8 weeks or so.
[Who]: Who built it, which has “fc 1” or similar for released software.
Desc: Additional description.
Copyright (c) 1986-1995 by cisco Systems, Inc.
Compiled Thu 09-Mar-95 23:54 by tli
Image text-base: 0x00001000, data-base: 0x00463EB0
Copyright, compilation date, by whom, as well as the starting address of the image.
ROM: System Bootstrap, Version 5.0(7), RELEASE SOFTWARE
ROM: GS Software (GS7), Version 10.0(7), RELEASE SOFTWARE (fc1)
The version of ROM bootstrap software, and the version of IOS in ROM.
demo.cisco.net uptime is 2 weeks, 4 days, 18 hours, 38 minutes
System restarted by reload
How long the router has been up, and why it restarted.
System image file is “sse-current”, booted via flash
How the router was booted.
RP (68040) processor with 16384K bytes of memory.
Type of processor.
G.703/E1 software, Version 1.0.
X.25 software, Version 2.0, NET2, BFE and GOSIP compliant.
Bridging software.
ISDN software, Version 1.0.
Various software options compiled in.
1 Silicon Switch Processor.
2 EIP controllers (8 Ethernet).
2 FSIP controllers (16 Serial).
1 MIP controller (1 T1).
8 Ethernet/IEEE 802.3 interfaces.
16 Serial network interfaces.
128K bytes of non-volatile configuration memory.
4096K bytes of flash memory sized on embedded flash.
Hardware configuration.
Configuration register is 0x102
Lastly, the “configuration register”, which may be set via software in recent release.