TechLeague

    Networking

    OSPF vs IS-IS: which IGP for your enterprise in 2026

    TechLeague Editorial··8 min read

    Most enterprises run OSPF. Most service providers run IS-IS. Knowing why helps you pick the right tool when you're free to choose.

    OSPF

    • Areas, ABRs, ASBRs; well-known, hires easy.
    • Runs on IP — encapsulation tightly coupled.

    IS-IS

    • Levels (L1/L2), runs on CLNS — independent of IP.
    • Scales effortlessly, fewer corner cases at large scale.

    Scaling

    • IS-IS handles thousands of routers cleanly.
    • OSPF scales fine to most enterprises.

    Operational

    • More OSPF talent in the market.
    • IS-IS quieter, but harder to find experts.

    Decision

    • Stick with OSPF unless you operate at SP scale.
    • If building EVPN-VXLAN underlay, IS-IS or eBGP both shine.

    Train IGP design reasoning in a TechLeague tournament.