IS-IS is categorised under Link State type of protocols & it is based on Dijkstra Algorithm same as OSPF. Admin Distance defaults to 115 & metric is 10 for all type of links (contrast to OSPF which has different cost for different type of media). It was originally standardized by ISO in 1987 (ISO10589) which was later adopted for TCP/IP type of networks & was called as Integrated IS-IS under RFC1195 (1990). Integrated/Dual IS-IS supports IP Routing while original IS-IS only supported CLNP routing. It supports both ISO’s Connectionless-Mode Network Service (CLNS) and IP. IS-IS runs on Layer2 in contrast to OSPF which … Continue reading A brief flashback of IS-IS – Part I