OSPF BSCI Module Lesson - Review of OSPF Fundamentals and Features BSCI © 2008 Cisco Systems, Inc All rights reserved Cisco Confidential CCNP – BSCI Bachkhoa Networking Academy Objective Link-State Routing Protocols Overview of OSPF Operations OSPF Data Structures OSPF Adjacency Database OSPF Area Structure OSPF Router Types OSPF Terminology Calculation the OSPF Metric Link-State Data Structure BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com CCNP – BSCI Bachkhoa Networking Academy Link-State Protocols Each router has a full picture of the network topology, including bandwidth information for links to remote networks Therefore, each router is able to independently select a loop-free and efficient pathway, based on cost, to reach every network in the area OSPF is a classless routing protocol Support VLSM Support Discontigous BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Routers with link-state routing protocols use a Hello protocol to discover any neighbors on its links A neighbor is any other router that is enabled with the same link-state routing protocol BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Sending Hello Packets to Neighbors Connected interfaces that are using the same link state routing protocols will exchange hello packets Once routers learn it has neighbors they form an adjacency –2 adjacent neighbors will exchange hello packets –These packets will serve as a keep alive function BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Building the Link State Packet Each router builds its own Link State Packet (LSP) Contents of LSP: –State of each directly connected link BSCI Học viện mạng Bach Khoa - © 2008 Cisco Systems, Inc All rights reserved –Includes information about neighbors such as neighbor ID, link type, & bandwidth Website: www.bkacad.com CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Directly Connected Networks Link: this is an interface on a router Link state: this is the information about the state of the links BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Flooding LSPs to Neighbors Once LSP are created they are forwarded out to neighbors –After receiving the LSP the neighbor continues to forward it throughout routing area BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved CCNP – BSCI Bachkhoa Networking Academy Link-State Routing BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved CCNP – BSCI Bachkhoa Networking Academy Link-State Routing Determining the shortest path –The shortest path to a destination determined by adding the costs & finding the lowest cost BSCI Học viện mạng Bach Khoa - Website: www.bkacad.com © 2008 Cisco Systems, Inc All rights reserved 10 CCNP – BSCI Bachkhoa Networking Academy OSPF Area Structure To reduce the SPF calculations, link-state routing protocols can partition networks into sub-domains called areas An area is a logical collection of OSPF networks, routers, and links that have the same area identification BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 17 CCNP – BSCI Bachkhoa Networking Academy OSPF Area Structure OSPF area characteristics: • Minimizes routing table entries • Localizes impact of a topology change within an area • Detailed LSA flooding stops at the area boundary • Requires a hierarchical network design BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 18 CCNP – BSCI Bachkhoa Networking Academy OSPF Router Types BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 19 CCNP – BSCI Bachkhoa Networking Academy Area Terminology • Routers A and B are backbone routers • Backbone routers make up area • Routers C, D, and E are known as area border routers (ABRs) • ABRs attach all other areas to area BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 20 CCNP – BSCI Bachkhoa Networking Academy OSPF Terminology BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 21 CCNP – BSCI Bachkhoa Networking Academy OSPF Calculation Routers find the best paths to destinations by applying Dijkstra’s SPF algorithm to the link-state database as follows: –Every router in an area has the identical link-state database –Each router in the area places itself into the root of the tree that is built –The best path is calculated with respect to the lowest total cost of links to a specific destination –Best routes are put into the forwarding database (routing table) BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 22 CCNP – BSCI Bachkhoa Networking Academy SPF Calculation Assume all links are Ethernet, with an OSPF cost of 10 BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 23 CCNP – BSCI Bachkhoa Networking Academy Link-State Data Structures: LSA Operation BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 24 CCNP – BSCI Bachkhoa Networking Academy Activity 3.1.2 Check Box: RIPv1 versus OSPF –Upon completion of this activity, the student will be able to compare routing issues between RIPv1 and OSPF 3.1.6 Drag and Drop: OSPF Router Types –Upon completion of this activity, the student will be able to identify the four different types of OSPF routers BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 25 CCNP – BSCI Bachkhoa Networking Academy Self Check Compare DV with LS Which multicast address LSA use How many table are there in OSPF, name it List two level hierarchy area in OSPF List types of OSPF router BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 26 CCNP – BSCI Bachkhoa Networking Academy Summary –Link-state routing protocols respond quickly to changes, send triggered updates when changes occur, and send periodic updates every 30 minutes –A two-tier hierarchical network structure is used by OSPF in which the network is divided into areas This area structure is used to separate the LSDB into more manageable sizes –Adjacencies are built by OSPF routers using the Hello protocol Over these logical adjacencies, LSUs are sent to exchange database information between adjacent OSPF routers BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 27 CCNP – BSCI Bachkhoa Networking Academy Summary (Cont.) –Dijkstra’s SPF algorithm is used to calculate best paths for all destinations SPF is run against the LSDB, and the outcome is a table of best paths, known as the routing table –After an LSA entry ages, the router that originated the entry sends an LSU about the network to verify that the link is still active The LSU can contain one or more LSAs BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 28 CCNP – BSCI Bachkhoa Networking Academy Q and A BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 29 CCNP – BSCI Bachkhoa Networking Academy Resources OSPF Support Page http://www.cisco.com/en/US/tech/tk365/tk480/ tsd_technology_support_sub-protocol_home.html Designing Large-Scale Internetworks http://www.cisco.com/en/US/tech/tk1330/ technologies_design_guide_chapter09186 a008075ac71.html#wp3548 OSPF Design Guide http://www.cisco.com/warp/public/104/1.html BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 30 CCNP – BSCI BSCI © 2008 Cisco Systems, Inc All rights reserved Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com 31 ... Link-State Routing Protocols Overview of OSPF Operations OSPF Data Structures OSPF Adjacency Database OSPF Area Structure OSPF Router Types OSPF Terminology Calculation the OSPF. .. Academy Activity 3. 1.2 Check Box: RIPv1 versus OSPF –Upon completion of this activity, the student will be able to compare routing issues between RIPv1 and OSPF 3. 1.6 Drag and Drop: OSPF Router... Resources OSPF Support Page http://www.cisco.com/en/US/tech/tk365/tk480/ tsd_technology_support_sub-protocol_home.html Designing Large-Scale Internetworks http://www.cisco.com/en/US/tech/tk 133 0/