Editing Cisco IOS (section)

== Packages and feature sets ==
IOS is shipped as a unique file that has been compiled for specific Cisco network devices. Each IOS Image therefore include a feature set, which determine the command-line interface (CLI) commands and features that are available on different Cisco devices. Upgrading to another feature set therefore entails the installation of a new IOS image on the networking device and reloading the IOS operating system. Information about the IOS version and feature-set running on a Cisco device can be obtained with the ''show version'' command.<ref name="auto"/>
 
Most Cisco products that run IOS also have one or more "feature sets" or "packages", typically eight packages for Cisco routers and five packages for Cisco network switches. For example, Cisco IOS releases meant for use on [[Catalyst switch]]es are available as "standard" versions (providing only basic IP routing), "enhanced" versions, which provide full [[IPv4]] routing support, and "advanced IP services" versions, which provide the enhanced features as well as [[IPv6]] support.<ref name="train" />

Beginning with the 1900, 2900 and 3900 series of ISR Routers, Cisco revised the licensing model of IOS.{{citation needed|date=March 2019}} To simplify the process of enlarging the feature-set and reduce the need for network operating system reloads, Cisco introduced universal IOS images, that include all features available for a device and customers may unlock certain features by purchasing an additional [[software license]].<ref>{{cite book |title=IP Routing on Cisco IOS, IOS XE, and IOS XR: An Essential Guide to Understanding and Implementing IP Routing Protocols |author1=Brad Edgeworth |author2=Aaron Foss |author3=Ramiro Garza Rios |year=2014 |publisher=Cisco Press |isbn= 9780133846768 |page=3 }}</ref> The exact feature set required for a particular function can be determined using the [http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp Cisco Feature Navigator]. Routers come with IP Base installed, and additional feature pack licenses can be installed as bolt-on additions to expand the feature set of the device. The available feature packs are:

* '''Data''' adds features like BFD, IP SLAs, IPX, L2TPv3, Mobile IP, MPLS, [[SCTP]].
* '''Security''' adds features like VPN, Firewall, IP SLAs, NAC.
* '''Unified Comms''' adds features like CallManager Express, Gatekeeper, H.323, IP SLAs, MGCP, SIP, VoIP, CUBE(SBC).

IOS images can not be updated with [[software bug]] fixes. To patch a vulnerability in IOS, a binary file with the entire operating system needs to be loaded.<ref>{{cite book |title=IP Routing on Cisco IOS, IOS XE, and IOS XR: An Essential Guide to Understanding and Implementing IP Routing Protocols |author1=Brad Edgeworth |author2=Aaron Foss |author3=Ramiro Garza Rios |year=2014 |publisher=Cisco Press |isbn= 9780133846768 |page=4 }}</ref>