Cisco IOS release naming

Most probably you already know this, but for those who are interested, here is a list of the letter definitions for Cisco IOS release trains. In more human terms, if you have loaded an IOS image like c2900-universalk9-mz.SPA.150-1.M5.bin, what those letters (in this case SPA) mean:

  • A = Aggregation/Access Server/Dial technology
  • B = Broadband
  • C = Core routers (11.1CA, 11.1CT, 11.1CC)
  • D = xDSL technology
  • E = Enterprise feature set
  • F = Feature Specific enhancements (11.2F)
  • G = Gigabit Switch Routers (GSR)
  • H = SDH/SONET technology (11.3HA)
  • J = Wireless Networking technology (Aironet)
  • M = Mobile (Restricted to Mobile Wireless BU usage and further reserved for Mainline)
  • N = Voice, Multimedia, Conference (11.3NA)
  • P = Platform features (11.2P)
  • R = Reserved for ROMMON reference
  • S = Service Provider
  • T = Reserved for Consolidated Technology Train
  • W = LAN Switching/Layer 2 routing
  • X = A short lived, one-time release (12.0XA)
  • Y = A short-lived, one-time release (when Xs are exhausted)
  • Z = A short-lived, one-time release (reserved if Ys are exhausted)

Additional information can be found here.

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Calin is a network engineer, with more than 20 years of experience in designing, installing, troubleshooting, and maintaining large enterprise WAN and LAN networks.

One thought on “Cisco IOS release naming”

  1. I believe SPA stands for Shared Port Adaptor, and are not flags of S P A and each of those corresponding features.

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