Cisco IOS Software Technical Documents
Documentation for each release of Cisco IOS Software
http://www.cisco.com/univercd/cc/td/doc/product/software/index.htm


Cisco IOS Version.................: 12.4(7a)T1

Maintenance Release Number-------------| || ||
Individual Release Number----------------|| ||
Numbered Version Identifier---------------| ||
New Feature Release Identifier--------------||
Numbered Version Identifier------------------|

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Cisco IOS Packaging
http://www.cisco.com/en/US/products/sw/iosswrel/ps5460/index.html

Four packages are designed to satisfy requirements in four typical service
categories:
	o IP data
	o Converged voice and data
	o Security and VPN
	o Enterprise protocols

Three additional premium packages offer new Cisco IOS Software feature
combinations that address more complex network requirements. All features
merge in the Advanced Enterprise Services package that integrates support
for all routing protocols with Voice, Security, and VPN capabilities.

Feature inheritance is another powerful aspect of Cisco IOS Packaging. After a
feature is introduced, it is included in the more comprehensive packages. The
feature inheritance facilitates migration by clarifying the feature content of
the different packages and how they relate to each another.

Cisco IOS Packaging also simplifies image naming. Each name is designed to
effectively convey the high-level feature content of, and the inheritance
characteristics for the new packages.

These categories summarize the new naming convention:
o Base—entry level image (IP Base, Enterprise Base)
o Services—addition of IP Telephony Service, MPLS, Voice over IP (VoIP),
  Voice over Frame Relay (VoFR), and ATM (SP Services, Enterprise Services)
o Advanced—addition of VPN, Cisco IOS Firewall, 3DES encryption, SSH, Cisco
  IOS IPsec and Intrusion Detection Systems (IDS) (Advanced Security, Advanced
  IP Services)
o Enterprise—addition of multi-protocols, including IBM, IPX, AppleTalk
  (Enterprise Base, Enterprise Services)

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IOS Releases

IOS is developed in a unique method at Cisco. Each major "train" or mainline
release of software (10.3, 11.2, 12.0, ...) combines support for features,
interfaces, and platforms that aren't always available on the previous train.
For 11.2.x software, the number x refers to a maintenance release designed to
fix or enhance existing features. IOS is backwards-compatible with older
versions, so an 11.2 router will talk to a router running 9.1; however, the
syntax on the command line will be drastically different. For certification
study, you should attempt to get at least 11.2.x code. Several changes were
made to the syntax around access lists, saving configurations, and several
other important items.