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  • IOS: Traditional, shared memory space, do not support symmetric multiprocessing.
  • IOS-XE: Linux Kernel, IOS like, for ISR, supports symmetric multiprocessing, separate memory space.
  • IOS-SR: Based on QNX Neutrino Microkernel from Blackberry, Unix Like, totally different than IOS, intended for Service Providers
  • NX-OS: Linux Kernel, Python supported, Modules loaded as needed, x64.

Ideal for lab on GNS3/EVE-NG:

  • IOSv - L2 or L3 official VIRL images.
  • IOU - L2 or L3 leaked images from Cisco's internal development.
  • C3725, C3745 and C7200 - Recommended C7200 as it supports IOS 15.