IS-IS
IS-IS is the IGP of choice in most Tier-1 and Tier-2 carrier networks and large-scale DC fabrics (Meta, Amazon). It runs under BGP in many hyperscale designs. Essential for service provider and large-scale DC networking roles.
What It Defines
Intermediate System to Intermediate System (IS-IS) is a link-state IGP running directly over L2, with no IP dependency. Level 1/Level 2 hierarchy mirrors OSPF areas. Widely preferred over OSPF in large service provider cores for its stability, scalability, and faster convergence. ISO 10589 is the base spec; RFC 5308 adds IPv6 support.
Canonical (Normative)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
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