BigIron RX Series Configuration Guide 85753-1001986-01Chapter28Configuring IS-IS (IPv4)The Intermediate System to Intermediate System (IS-IS) protocol is a link-state Interior GatewayProtocol (IGP) that is based on the International Standard for Organization/InternationalElectrotechnical Commission (ISO/IEC) Open Systems Internet Networking model (OSI). In IS-IS, anintermediate system (router) is designated as either a Level 1 or Level 2 router. A Level 1 routerroutes traffic only within the area in which the router resides. A Level 2 router routes trafficbetween areas within a routing domain.The Brocade implementation of IS-IS is based on the following specifications and draftspecifications:• ISO/IEC 10589 – “Information Technology – Telecommunication and information exchangebetween systems – Intermediate system to Intermediate system intra-domain routinginformation exchange protocol for use in conjunction with the protocol for providing theconnection less-mode Network Service (ISO 8473)”, 1992• ISO/IEC 8473 – “Information processing systems – Data Communications – Protocols forproviding the connectionless-mode network service”, 1988• ISO/IEC 9542 – “Information Technology – Telecommunication and information exchangebetween systems – End system to Intermediate system intra-domain routing informationexchange protocol for use in conjunction with the protocol for providing the connectionless-mode Network Service (ISO 8473)”, 1988• RFC 1195 – “Use of OSI IS-IS for Routing in TCP/IP and Dual Environments”, 1990.• RFC 2763 – “Dynamic Host Name Exchange Mechanism for IS-IS”, 2000.• RFC 2966 – “Domain-wide Prefix Distribution with Two-Level IS-IS”, 2000• Portions of the Internet Draft “IS-IS extensions for Traffic Engineering”draft-ieff-isis-traffic-02.txt (dated 2000) that describe the Extended IP reachability TLV (TLVtype 135) and the extended Intermediate System (IS) reachability TLV (TLV type 22). Theseportions provide support for the wide metric version of IS-IS. No other portion is supported onBrocade’s implementation of IS-IS.NOTEThe BigIron RX does not support routing of Connectionless-Mode Network Protocol (CLNP) packets.The device uses IS-IS for TCP/IP only.Relationship to IP route tableThe IS-IS protocol has the same relationship to the device’s IP route table that OSPF has to the IProute table. The IS-IS routes are calculated and first placed in the IS-IS route table. The routes arethen transferred to the IP route table.The protocol sends the best IS-IS path for a given destination to the IP route table for comparison tothe best paths from other protocols to the same destination. The CPU selects the path with thelowest administrative distance and places that path in the IP route table.
