The paper focuses primarily on the research of IGP routing protocols, namely RIP, EIGRP and OSPF from the point of view of the convergence time in small and medium-sized networks. Experiments using GNS3 and in real routed networks are shown for both IPv4 and IPv6 protocols and their results are described in detail. The results demonstrate EIGRP as the fastest converging protocol closely followed by OSPF while RIP convergence is much slower. Also, the data traffic generated by all three protocols were compared. Here, RIP is the best while EIGRP and OSPF generated 5–6 times more data in the beginning and 2–3 times more later. The comparison of simulated results shows that routing protocol behavior in GNS3 differ significantly from real routers. Corresponding results were obtained for both IPv4 and IPv6 and both are presented. The difference between IPv4 and IPv6 are not significant. On the other hand, significant difference has been observed between the corresponding experiments in GNS3-simulated and real networks.