Cisco IOS is described as '(originally Internetwork Operating System) is a family of software used on most Cisco Systems routers and current Cisco network switches. (Earlier switches ran CatOS'. There are six alternatives to Cisco IOS for a variety of platforms, including Linux, Self-Hosted solutions, VMware Workstation, GNS3 and VMware Player. The best alternative is MikroTik RouterOS. It's not free, so if you're looking for a free alternative, you could try ZEVENET or Quagga. Other great apps like Cisco IOS are VyOS (Paid, Open Source), Junos OS (Paid) and securityrouter.org (Freemium).
Our products are based under the unique terms of no limitations and no vendor lock-in technology in order to provide the best performance, high support level directly from the vendor, development agility in order to be integrated with any application or infrastructure and...
Quagga is a network routing software suite providing implementations of Open Shortest Path First (OSPF), Routing Information Protocol (RIP), Border Gateway Protocol (BGP) and IS-IS for Unix-like platforms, particularly Linux, Solaris, FreeBSD and NetBSD.
The securityrouter.org project is a network operating system and software distribution based on OpenBSD, featuring a single, revision-managed, clear-text configuration file with soft re-configuration, editable from CLI and web interface.