OSPF - A comparison with IS-IS
Both IS-IS and OSPF are excellent routing protocols, and each has its own strengths.
IS-IS is more flexible than OSPF in terms of topology because it doesn’t have the backbone area 0 restriction. This makes IS-IS easier to manage in large, complex networks. It also has a slight advantage in terms of scalability due to its more efficient handling of link-state advertisements (LSAs).
Secondly, IS-IS is designed to function at the Network Layer of the OSI model, but unlike OSPF, it operates independently of the IP protocol. In other words, it doesn’t use IP to exchange IS-IS messages between routers.
However, OSPF is more widely used and understood, which can make it easier to find support and resources for troubleshooting. OSPF also integrates better with IP, which is the dominant network protocol and is therefore often a more convenient choice.
In terms of performance, both protocols are very similar, and the choice between them often comes down to the specific needs and constraints of your network, as well as personal preference and familiarity.
It is true that for large Internet Service Provider (ISP), IS-IS is the preferred IGP due to its scalability and flexibility advantages, but OSPF is also widely used and perfectly capable.
It’s also worth noting that both of these protocols can coexist in the same network, so you don’t necessarily have to choose one or the other.
Links:
https://forum.networklessons.com/t/integrated-is-is-configuration-on-cisco-ios/1736/20?u=lagapidis