The trains are used to map distinct markets or groups of customers that Cisco is targeting. The different IOS trains are as follows:
1. The mainline TRAIN is designed to be the most stable release.
2. The T - Technology train gets new features and bug fixes THROUGHOUT its life, and is less stable than the mainline train. Cisco does not recommend this train for production environment.
3. The S - Service Provider train is customized for the Service Provider customers.
4. The E - Enterprise train is customized for implementation in enterprise environments.
5. The B - broadband train SUPPORTS Internet-based broadband features.

The trains are used to map distinct markets or groups of customers that Cisco is targeting. The different IOS trains are as follows:
1. The mainline train is designed to be the most stable release.
2. The T - Technology train gets new features and bug fixes throughout its life, and is less stable than the mainline train. Cisco does not recommend this train for production environment.
3. The S - Service Provider train is customized for the Service Provider customers.
4. The E - Enterprise train is customized for implementation in enterprise environments.
5. The B - broadband train supports Internet-based broadband features.