cisco ios version guide

IOS version numbers are formatted as follows: x.y(z)t The "x" designates a major revision number. The "y" designates a minor revision number. The "z" designates an individual release number The “t” designates a train identifier. Thus, the third release of IOS version 12.4 would be identified as 12.4(3). The major and minor revision numbers combined is often called the Maintenance Release number (for example, “12.4”). Trains identify IOS releases to specific markets, and are represented by a single letter: • The “T” or Technology train is continuously updated with new features and security fixes. • The “E” or Enterprise train contains features and commands for enterprise-level equipment. • The “S” or Service Provider train contains features and a command-set for specific ISP equipment The absence of a train identifier denotes a…
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