Cisco IOS!

The main product of MikroTik is a Linux-based operating system known as MikroTik RouterOS. Installed on a personal computer or server computer, it turns the computer into a network router, implementing features such as firewall rules, virtual private network (VPN) server and client, bandwidth shaping and quality of service, wireless access point functions and other commonly used features for routing and interconnecting networks. The system is also able to serve as a captive-portal-based hotspot system. The operating system is licensed in increasing service levels, each releasing more of the available RouterOS features. A Windows software application called Winbox provides a graphical user interface for the RouterOS configuration and monitoring, but the software also allows connections via FTP, telnet, and secure shell (SSH). An application programming is available for direct access from custom applications for management and monitoring. »

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.

Junos OS (more formally Juniper Network Operating System) is the FreeBSD-based operating system used in Juniper Networks hardware routers.It is an operating system that is used in Juniper's routing, switching and security devices. Juniper offers a Software Development Kit (SDK) to partners and customers to allow additional customization. The biggest competitor of Junos is Cisco Systems' IOS.Junos OS was formerly branded as Juniper Junos, and is commonly referred to as simply Junos, though this is a general brand name of Juniper Networks, including other product lines such as Junos Fusion. »