© 2008 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialBSCI 1 BSCI Module 3 Lesson 4 - OSPF Network Types OSPF © 2008 Cisco Systems, Inc. All rights reserved.BSCI 2 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Objective  OSPF Network Types  Adjacency Behavior for a Point-to-Point Link  Adjacency Behavior for a Broadcast Link  Selecting the DR and BDR  Adjacency Behavior for a NBMA Network  DR Election in NBMA Topology  OSPF Over Frame Relay  OSPF over NBMA Topology Modes © 2008 Cisco Systems, Inc. All rights reserved.BSCI 3 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Different Network Types and OSPF  There are three distinct classifications of physical network media that OSPF can differentiate between. Each of these network types requires a slightly different configuration to optimize the performance of OSPF.  Cisco IOS Software allows five main network types to be configured, as displayed in Table 5-5. © 2008 Cisco Systems, Inc. All rights reserved.BSCI 4 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com OSPF Network Types © 2008 Cisco Systems, Inc. All rights reserved.BSCI 5 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Configuring the Network Type  OSPF is highly adaptable. Consider its capability to accommodate either broadcast or nonbroadcast multiaccess (NBMA) network types. OSPF responds accordingly by altering its operation to reflect the configuration that you have given it. © 2008 Cisco Systems, Inc. All rights reserved.BSCI 6 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Broadcast Networks  Set an interface to operate in broadcast network mode when the network is a fully meshed.  When this command is applied to an interface, OSPF elects a DR/BDR, builds an adjacency with the DR, and builds neighbor relationships with all other OSPF routers in the network. © 2008 Cisco Systems, Inc. All rights reserved.BSCI 7 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Nonbroadcast Networks  When configuring an interface as nonbroadcast, OSPF cannot perform multicasting on that link.  Lack of multicast functionality impacts OSPF’s operation because OSPF Hellos cannot be properly transmitted.  Physical Frame Relay interfaces and multipoint subinterfaces are recognized as nonbroadcast by default. The following alternatives allow you to make OSPF operate when a nonbroadcast type network is encountered: –Change the network type of OSPF. This is the easiest change but is not possible in every instance. –Manually define the neighbors. This forces adjacencies that are created by sending unicast Hello packets. –Alter the behavior of the Layer 2 protocol. © 2008 Cisco Systems, Inc. All rights reserved.BSCI 8 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Nonbroadcast Networks © 2008 Cisco Systems, Inc. All rights reserved.BSCI 9 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Point-to-Multipoint Networks  OSPF point-to-multipoint interfaces are defined as numbered point-to- point subinterfaces, with the router having one or more OSPF neighbors.  An OSPF point-to-multipoint network has the following benefits compared to nonbroadcast multiaccess and point-to-point networks: –Point-to-multipoint is easier to configure because it requires no configuration of neighbor commands. Point-to-multipoint connections consume only one IP subnet and require no designated router election process. –Point-to-multipoint has a fully or partial meshed topology. –Point-to-multipoint can be more reliable in fully meshed networks because it maintains connectivity in case of virtual circuit failure. –When you configure the OSPF network type as point-to- multipoint, routing between two routers not directly connected goes through the router (hub) that has virtual circuits to both routers (spokes). © 2008 Cisco Systems, Inc. All rights reserved.BSCI 10 CCNP – BSCI Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com Point-to-Multipoint Networks [...]... Topology Modes of Operation  RFC 232 8-compliant modes are as follows: –Nonbroadcast (NBMA) –Point-to-multipoint  Additional modes from Cisco are as follows: –Point-to-multipoint nonbroadcast –Broadcast –Point-to-point Router(config-if)# ip ospf network [{broadcast | non-broadcast | point-tomultipoint [non-broadcast] | point-to-point}]  This interface command defines OSPF network type BSCI © 2008 Cisco... Bachkhoa Networking Academy Point-to-Point Networks  When you configure an interface as an OSPF point-to-point network type, this command understands that the only other OSPF- speaking router on that interface is directly connected  As previously mentioned, the following methods can be used to get OSPF to operate in such a configuration: –Use point-to-point subinterfaces –Use a physical interface and an OSPF. .. OSPF network type BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 19 CCNP – BSCI Bachkhoa Networking Academy Activity  3. 4.1 Drag and Drop: OSPF Network Types –Upon completion of this activity, the student will be able to identify the different OSPF network types  3. 4.4 Checkbox: DR and BDR Election –Upon completion of this activity, the student will be able... interface and an OSPF point-to-point network type BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 11 CCNP – BSCI Bachkhoa Networking Academy Adjacency Behavior for a Point-to-Point Link  Hello time 10s, Dead time 40  Neighboring routers become adjacent whenever they can communicate directly  Usually, the IP source address of an OSPF packet is set to the... Bách Khoa - www.bkacad.com 16 CCNP – BSCI Bachkhoa Networking Academy DR Election in NBMA Topology BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 17 CCNP – BSCI Bachkhoa Networking Academy OSPF Over Frame Relay BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 18 CCNP – BSCI Bachkhoa Networking Academy OSPF over... Bách Khoa - www.bkacad.com 12 CCNP – BSCI Bachkhoa Networking Academy Adjacency Behavior for a Broadcast Link  Reduce routing update traffic  Manage link-state synchronization  Note: After a DR and BDR have been selected, any router added to the network establishes adjacencies with the DR and BDR only BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 13 CCNP... Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 20 CCNP – BSCI Bachkhoa Networking Academy Q and A BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 21 CCNP – BSCI BSCI © 2008 Cisco Systems, Inc All rights reserved Bachkhoa Networking Academy Học viện mạng Bách Khoa - www.bkacad.com 22 ... The BDR uses the wait timer to determine whether the DR is out of service BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 15 CCNP – BSCI Bachkhoa Networking Academy Adjacency Behavior for a NBMA Network Hello Time 30 s; Dead Time 120s  If the NBMA topology is not fully meshed, a broadcast or multicast sent by one router will not reach all the other routers ... Bách Khoa - www.bkacad.com 13 CCNP – BSCI Bachkhoa Networking Academy Selecting the DR and BDR  It is more efficient to have one router represent the other routers to a new router rather than all the routers pass the same information BSCI © 2008 Cisco Systems, Inc All rights reserved Học viện mạng Bách Khoa - www.bkacad.com 14 CCNP – BSCI Bachkhoa Networking Academy Setting Priority for DR election . follows: –Point-to-multipoint nonbroadcast –Broadcast –Point-to-point ip ospf network [{broadcast | non-broadcast | point-to- multipoint [non-broadcast] | point-to-point}]  This interface command defines OSPF. mạng Bách Khoa - www.bkacad.com Point-to-Point Networks  When you configure an interface as an OSPF point-to-point network type, this command understands that the only other OSPF- speaking router. Bách Khoa - www.bkacad.com Point-to-Multipoint Networks  OSPF point-to-multipoint interfaces are defined as numbered point-to- point subinterfaces, with the router having one or more OSPF neighbors. 