51CTO下载-Module 9 - ISIS Routing.ppt

IS-IS Configuration Module 9 IS-IS Overview Module 9, Lesson 1 Lesson Objectives Review IS-IS terminology Compare IS-IS to OSPF Review IS-IS operations Discuss IS-IS NET format Intermediate System – Intermediate System International Standards Organization (ISO) Open System Interconnect (OSI) standard for routing Originally developed for CLNP/CLNS – adapted for TCP/IP Link-state protocol Routers advertise local links only Each router builds a database of all links in the area, then calculates own routing table Hierarchical routing protocol Summarize routes based on areas OSPF and IS-IS – the Similarities Interior gateway protocols that maintain link state databases and calculate SPF Sends updates only when there is a change in the network Classless protocol, supports VLSM Uses HELLO packets to form/maintain adjacencies Operational details (timers, etc.) differ Hierarchical topology Summarizes addresses OSPF versus IS-IS OSPF Single backbone area Border routers are in two areas simultaneously – defined by interface Terminology – internal router, ABR Metric is cost IS-IS No backbone area required A router is entirely within a single area – area borders are links, not routers Terminology – Level 1, Level 2 4 metrics – default, delay, expense, error IS-IS Terminology and Design Level 1 and Level 2 Routers IS-IS State Machine IS-IS Packets Hellos Track link state, form adjacencies LSPs Link state packets – contains link state information CSNP Complete Sequence Number PDU (Packet Data Unit) Description of entire link state database PSNP Partial Sequence Number PDU Used to request detailed LSP for specific link IS-IS Hellos (IIH) Point-to-point Uses ES-IS Hello to initialize link, then sends IIH Hello contains Source ID, Area Address, IS Type L1,L2 or L1L2 and Circuit ID Level 1 multicast: to address 0180.C200.0014 on broadcast nets Hello contains Source ID, Area Address, IS type, DIS priority, LAN ID, SystemID of the L1 DIS DIS – Designated Intermediate System i.e. Design