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LE-201 - Unicast Routing and L3 Switch Configuration Module 4 - 1 OSPF Overview and Configuration Module 4 OSPF Overview and Configuration.

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Presentation on theme: "LE-201 - Unicast Routing and L3 Switch Configuration Module 4 - 1 OSPF Overview and Configuration Module 4 OSPF Overview and Configuration."— Presentation transcript:

1 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Module 4 OSPF Overview and Configuration

2 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Module Objectives Define OSPF, features, advantages over RIP Describe OSPF LSA, format and Types Define LSDB, Initial synchronization, database exchange & reliable flooding Describe Routing Calculations, supported network type & Database Synchronization Describe how to build OSPF Networks Define the OSPF routing, areas, router types and virtual Links Differentiate DR, BDR, Router Election OSPF Configuration and Examples Lab Exercises Summary

3 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Define OSPF Dynamic Routing Protocol Link State Protocol Employ a distributed database model More efficient than RIP

4 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration The OSPF Advantage OSPF is an interior gateway protocol (IGP) that is more efficient than RIP. l Consumes fewer network resources l Highly scalable l Faster convergence l A more descriptive routing metric l Route load sharing l Greater security

5 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration distributed database model Employ a distributed database model. Each router advertises a description of its local environment l interfaces l costs l neighbor information LSDB Uses a single synchronized database for collecting advertisements (LSDB) Routing table is derived from this database Utilize a shortest-path first algorithm OSPF OSPF is a Link-state routing protocol Link-state Protocol

6 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Basic Features of OSPF Hello Packets Link State Advertisements (LSA) Link State Database Reliable Flooding Shortest Path First Routing Calculations Areas and Inter-area Routing

7 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Hello Packet & Neighbor Discover OSPF Hello OSPF Hello packets are sent out all of a router’s interfaces to advertise itself to neighbor routers A router learns about its neighbors when it receives neighbor router’s Hello packet 10 seconds Hello packets are sent out every 10 seconds by default 40 seconds If subsequent Hello packet is not received within 40 seconds, neighbor relationship is terminated

8 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Hello Packets Will only be recognized by routers attached to the same subnet with same subnet mask Contains information on parameters for l Hello Interval and l Router Dead Interval This information is used by neighbor routers to agree on the communication variables This allows an occasional lost Hello packet not to be interpreted as a link down condition.

9 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Hello Packets (cont.) In a broadcast environment, it contains the OSPF router IDs of all routers the sender has heard up to the point of transmission This reduces overhead of sending multiple Hellos Ensure that the OSPF link is bi-directional Ensure that the OSPF link is bi-directional l NOTE: An OSPF router will not forward data packets over a unidirectional link.

10 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Link State Advertisement (LSA) Each OSPF router is responsible for describing its local piece of the routing topology through the transmission of link- state advertisements. Every thirty minutes a router will -- even in the absence of any change, retransmit this self-originating data in the event it may have been lost or corrupted in a neighbor router’s tables.

11 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF LSA Format All OSPF LSAs start with a 20-byte common header This provides orderly updating and removal of LSAs and organization to the LSDB

12 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - LS Age Number of seconds since the LSA was originated normally mins. If LSA reaches 30 minutes, originating router will refresh the LSA by flooding a new instance. If LSA reaches 1 hour, it is deleted from the database.

13 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - LS Type Classifies the LSA according to function l Type 1 l Type 2 l Type 3 l Type 4 l Type 5 l Type 7

14 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - Link State ID A unique identification Used to describe a router in the OSPF routing domain Depends on the LS Type l Type 1, 2, 3, 4, 5 or 7

15 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - Advertising Router The originating router’s OSPF router ID In practice, this is one of the router’s IP address

16 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - LS Sequence Number A linear sequence number Used to compare a new LSA with an old LSA The LSA instance having the larger LS Sequence Number is considered to be more recent.

17 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Format - LS Checksum Used to detect data corruption. Does not include LS Age field Derived using Fletcher checksum algorithm

18 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LSA Types Type NumberDescription 1Router-LSAs 2Network-LSAs 3Summary-LSAs (IP network) 4Summary-LSAs (ASBR) 5AS external-LSAs 7NSSA external-LSAs

19 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 1 - Router-LSAs Generated by each OSPF router It describes the router’s set of active interfaces, its associated cost and any neighbor information Link State ID is set to the router’s OSPF Router ID Flooded throughout a single area only

20 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 2 - Network-LSAs Generated by OSPF Designated Routers (DRs) Describes a network segment - i.e., broadcast domain along with the IDs of all currently attached routers. Link State ID field lists the IP interface address of the DR

21 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 3 - Summary-LSAs (IP Network) This originate from Area Border Routers (ABRs) OSPF areas Supports hierarchical routing through the use of OSPF areas Link State ID field is an IP network number

22 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 4 - Summary-LSAs (ASBR) This originate from Area Border Routers (ABRs) Similar to LS Type 3 Used when destination is an Autonomous System Boundary Router (ASBR) The Link State ID is the AS boundary router’s OSPF Router ID

23 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 5 - AS-external-LSAs Originated by AS boundary routers and describes destinations ex-ternal to the AS. Link State ID field specify an IP network number

24 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration LS Type 7 - NSSA external-LSAs Allows the import of external routes that will not be advertised out of the NSSA NSSA - Not So Stubby Area

25 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Router LSA Format - Link ID Originating router’s link information follows the LSA header. There are four Link IDs determined by Link Type. l Type 1 Neighboring router’s Router ID Three of this Link ID are relevant in a broadcast network

26 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Router LSA Format - Link Data For transit and Virtual Links l specifies the IP address of associated router interface. For stub networks l Specifies the stub network mask

27 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Router LSA Format - Metric The cost of using this router link. A user-configurable value from ,535 The larger the metric, the less likely (more expensive) data will be routed over that particular link. Connections to STUB networks are allowed to advertise a metric of zero.

28 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Link-State Database (LSDB) The collection of all OSPF LSAs received Each OSPF router has an identical LSDB Gives complete description of the network: l routers l network segments l interconnectivity (how it is interconnected) LSDBs are exchanged between neighboring routers soon after routers discover each other Maintained through a procedure called reliable flooding

29 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration When two neighbors first start communicating, they must synchronize their databases before forwarding traffic over their shared link to prevent routing loops from occurring. LSDB Initial Synchronization

30 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF-specified Database Exchange Procedure used by the routers to synchronize their databases once the hello protocol determines a bi-directional connection between router neighbors. During synchronization, the neighbor routers do three things: l Forward current LSA headers l Compares the header received to the LSDB l Request the full LSA for new or newer headers

31 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example LSDB Initial Synchronization Switches A thru F are in a stable OSPF network and have fully synchronized databases OSPF is restarted on Switch F, forcing database synchronization with switch A.

32 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example LSDB Initial Synchronization

33 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Database - Reliable Flooding LSA Updates are periodically generated by a router wishing to update a self-originated LSA because: l The router’s local state may have changed l The router wants to delete one of its self- originated LSAs Used to propagate LSA Updates throughout the routing domain

34 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Reliable Flooding - What Happens A router will generate a Link-state Update packet containing one or more LSAs Update is forwarded out all interfaces. Neighbor router receives the Update and compares the LSAs with the LSDB More recent LSAs are installed in LSDB Acknowledgement is sent back to originating route New Link-state Update containing the LSA is sent out all interfaces except receiving one.

35 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Routing Calculations With router LSDBs synchronized for all routers in routing domain l The router will use Dijkstra’s Shortest Path First algorithm l This allows calculation of shortest paths to all destinations Routing table is constructed from the calculations and includes l network destinations l associated costs

36 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Routing Calculations Every link carries an associated cost.

37 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Routing Calculations

38 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Routing Calculations Applying Dijkstra’s SPF algorithm, Switch C’s routing table would incorporate the highlighted links Note that Switch A will never talk directly to Switch B as long as the links thru Switch C remain stable.

39 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Routing Calculations Note how changing a link cost affects the route calculation for the shortest path With this configuration, Switch C now has two paths of equal cost to communicate with Switch J. Communication with Switch B is no longer direct, but must routed thru Switch A.

40 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Network Types Point-to-Point networks l Serial lines Non-broadcast Multi-access (NBMA) networks l X.25, ATM Point-to-Multipoint networks l Frame Relay Broadcast networks

41 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Network Type - Broadcast Networks A network with more than two attached devices Has the ability to address a single physical message to all of the attached devices (broadcast)

42 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Network Type - Broadcast Networks Only network type supported by Extreme switches Other Network Types are for WAN use

43 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Broadcast Networks Terminology DR - Designated Router BDR - Backup DR DR and BDR Election Network LSAs

44 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Broadcast Networks - Designated Router Every broadcast network has a Designated Router (DR) and a Backup Designated Router (BDR) Each router on the network exchanges link state information only with the DR and BDR. l This information is used to maintain database synchronization between the DR and neighbor routers This reduces the amount of traffic otherwise consumed by routing protocol traffic Only a DR generates a LS Type 2 - Network- LSAs

45 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration DR and BDR Election First OSPF router on an IP subnet always becomes the DR Second OSPF router always becomes BDR If DR or BDR fail, the OSPF router with the highest Router Priority will replace the BDR If two OSPF routers have same Router Priority, then the OSPF Router ID will break the tie A Router Priority of 0 will prevent an OSPF router from ever being elected as DR or BDR

46 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Database Synchronization An OSPF router will send its Link State Update (LSU) to the DR and BDR l The destination IP address for the LSU will be multicast address (All DRouters). The DR will then flood the update to all OSPF routers l The destination IP address for the LSU will be multicast address (All OSPFRouters).

47 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Representing Broadcast Subnet in LSDB If an OSPF router included all known routers on a common subnet in its router-LSA, there would be n*(n-1) links in the OSPF database. Network-LSA By using a new LSA type, the Network-LSA, to represent the broadcast subnet, the number of links is reduced from n*(n-1) to n*2. Each network LSA has a link to every router- LSA, and every router-LSA has a link to the broadcast subnet’s network-LSA. DR maintains the network-LSA

48 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Type 2: Network LSAs Created in order to reduce the number of links in each router’s resulting LSDB Describes the subnet, all routers on that network DR identity

49 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Type 2: Network LSAs The network-LSA helps in database synchronization, since a router having a router- LSA with a link to the network-LSA and vice-versa is known to have a database synchronized with the Designated Router.

50 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Building OSPF Networks Hierarchical Routing OSPF Routing Hierarchy OSPF Areas OSPF Types of Routers Virtual Links CLI Commands for OSPF Configuration

51 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Hierarchical Routing OSPF implements a two-level hierarchical routing scheme Saves router memory consumed by the routing table Saves router resources when computing the routing table Saves link bandwidth when distributing routing data

52 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Defined OSPF Areas Defined The OSPF hierarchy is maintained through the deployment of OSPF areas 32-bit Area ID Each OSPF area is identified by a 32-bit Area ID Each area consists of a collection of one or more network segments interconnected by routers An area has its own LSDB consisting of router-LSAs and network-LSAs l These LSAs describe area’s topology flat Routing with an area is flat.

53 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Area’s Router-LSA and Network-LSA Not flooded beyond the area’s borders Detailed knowledge of area’s topology is hidden from all other areas in the parent Autonomous System. Area “A” does not know the internal topology of Area “B” and vice versa.

54 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Area Border Router (ABR) Manages inter-area communication Attached to two or more areas, running multiple copies of the basic algorithm Maintain LSDBs for each attached area and an additional copy for the backbone Type 3: Condense the topological information of their attached areas into Type 3: Summary- LSAs for distribution to the backbone. l The backbone in turn distributes the information to the other areas.

55 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Area Border Router (ABR) cont. ABRs can be configured to aggregate some or all of the networks within its dependent area into a single, summary network address with a less discreet network mask.

56 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Types of OSPF Areas Normal Area l Area 0 (Backbone) Stub Areas Not-So-Stubby-Areas (NSSA) Virtual Links

57 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Normal Area An area which is not a: l Stub area l NSSA Can be placed anywhere within the OSPF routing domain Support ASBRs Support Virtual Links Can distribute external routes

58 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Area 0 (Backbone) Is a Normal Area Responsible for distributing routing information between areas Consist of l all area border routers l networks not contained in any other area l and their attached routers Has an Area ID of Only one backbone area per AS All areas are required to attach directly to the OSPF backbone area

59 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Stub Area For routers with limited resources l reduce memory and computation requirements The LSDB is kept as small as possible External route information is not distributed l Will use default routes to ABRs instead Does not support ASBRs Does not support virtual links Appears to lie on the edge of an OSPF domain (AS) in configuration

60 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Not-So-Stubby-Area (NSSA) Similar to existing OSPF Stub Area with two additional capabilities l External routes originating from ASBR connect- ed to NSSA can be advertised within l External routes originating from NSSA can be propagated to other areas, including the backbone.

61 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Defines Three types of Routers Internal Router (IR) l Has all of its interfaces within the same area Area Border Router (ABR) Autonomous System Boundary Router (ASBR)

62 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Hierarchical Components OSPF Router Types Displayed ABR ASBR *All other routers that are not labeled ASBR or ABR are Internal Routers Internet

63 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Virtual Links Used when a new area is introduced that does not have a direct physical attachment to the backbone Provides a logical path between the ABR of the disconnected area and the backbone A virtual link is established between two ABRs that have a common area, with one ABR connected to the backbone

64 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF Configuration Example

65 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Configuring OSPF Must have a unique router ID for each switch Recommend manually setting the router ID of the switches participating in OSPF l Simplifies router management l Prevents corruption of virtual links Do not use as a router ID

66 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration OSPF CLI Commands enable/disable ospf config ospf add/delete vlan create/delete ospf area config ospf vlan area show ospf area show ospf interfaces

67 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - enable/disable ospf enable ospf disable ospf Enable or disable OSPF for the whole router. Default is disabled.

68 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf add/del vlan config ospf add vlan [ | all] config ospf delete vlan [ | all] l Enables or disables OSPF on one or all VLANs (router interfaces). l The default setting is disabled.

69 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - create/del ospf area create ospf area delete ospf area [ | all] l Create or delete an OSPF area. Area does not need to be created. It exists by default. It also cannot be deleted. l Once an OSPF area is removed, the associated OSPF area and OSPF interface information will also be removed.

70 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf vlan area config ospf vlan area l Associates a VLAN (router interface) with/from an OSPF area. The area must already be defined. All router interfaces must have an associated OSPF area. l By default, all router interfaces are associated with area (backbone).

71 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - show ospf show ospf l Displays global OSPF information. show ospf area { } l Displays information about a particular OSPF area, or all OSPF areas.

72 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example: show ospf area OSPF_Switch4: show ospf area Area: Stub: FALSE Rtr Id: Spf Runs: 48 Num ABR: 6 Num ASBR: 0 Num LSA: 43 LSA Chksum:0x Interfaces: IP addr Ospf State DR IP addr BDR IP addr /24 E DOWN /24 E BDR Inter-Area route Filter: None External route Filter: None Configured Address Ranges: Area: Stub: FALSE Rtr Id: Spf Runs: 21 Num ABR: 2 Num ASBR: 0 Num LSA: 35 LSA Chksum:0x16c3de Interfaces: IP addr Ospf State DR IP addr BDR IP addr /24 E DR Inter-Area route Filter: None External route Filter: None Configured Address Ranges:

73 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - show ospf interfaces show ospf interfaces {vlan | area |all} Displays information about one or all OSPF area, or all OSPF areas.

74 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example: show ospf interface Summit4: sh ospf interface Interface(rif4): /24 Vlan: norm151 Ospf: ENABLED Router: ENABLED AreaId: RtId: Cost: 1 Pri: 1 Transit Delay: 1 40s Hello Interval: 10s Rtr Dead Time: 40s Retransmit Interval: 5s Authentication: NONE State: BDR Number of events: 1 DR RtId: DR IP addr: BDR IP addr: Neighbours: RtrId: IpAddr: Pri: 1 State: FULL Dr: BDR: Dead Time: 7 RtrId: IpAddr: Pri: 1 State: FULL Dr: BDR: Dead Time: 6

75 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Laboratory Exercise Lab4 - OSPF Configuration I

76 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Lab4 - Network Topology

77 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration More OSPF Configuration config ospf add virtual-link config ospf delete virtual-link show ospf virtual-link

78 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf add virtual-link config ospf add virtual-link config ospf delete virtual-link l Adds or deletes a virtual link connected to another area border router (ABR). l Specify the following: l routerid -- Far-end router ID. l Areaid -- Transit area used for connecting the two end-points. The transit area cannot be the backbone ( ).

79 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - show ospf virtual-link show ospf virtual-link { | all} Displays virtual link information about a particular router or all routers. Default is all. Contains: l Area ID and neighbor router ID l Receive interval, transit delay, Hello interval, and dead interval. l Authentication configuration l Virtual link type and number of events l Neighbor router ID, IP address, and priority l Link state, DR ID, BDR ID, and dead time

80 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example: show ospf virtual-link OSPF_LAB_2:19 # show ospf virtual-link AreaId: NbrRouterId: Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40 Auth Type: NONE State: P2P Number of Events: 3 RtrId: IpAddr: Pri: 1 State: FULL Dr: BDR: Dead Time: 9 AreaId: NbrRouterId: Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40 Auth Type: NONE State: P2P Number of Events: 1 RtrId: IpAddr: Pri: 1 State: FULL Dr: BDR: Dead Time: 7

81 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Laboratory Exercise Lab5 - OSPF Configuration II

82 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Lab5 - Network Topology 1

83 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Lab5 - Network Topology 2

84 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration More OSPF Configuration - Areas config ospf area normal config ospf area stub config ospf area nssa show ospf

85 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf area normal config ospf area normal l Configure an OSPF area as a normal area l Default area type is normal l Area can only be normal

86 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf area stub config ospf area stub [summary|nosummary] stub-default-cost l Configures an OSPF area as a stub area. l Stub-default-cost is the the cost of the default summary-LSA that the router should advertise into the area

87 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf area nssa config ospf area nssa [summary|nosummary] stub-default-cost {translate} l Configures an OSPF area as a NSSA. l Stub-default-cost is the the cost of the default summary-LSA that the router should advertise into the area l Translate option: determines whether type 7 LSAs are translated into type 5 LSAs.

88 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - show ospf show ospf Display global OSPF information: l Router ID l OSPF state l Is router an autonomous system boundary router (Y/N)? l Is router an area border router (Y/N)? l Number of external LSAs processed l External LSA checksum l Number of originating new LSAs l Number of received new LSAs l Shortest Path First hold time

89 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example: show ospf Summit4: show ospf Router Id OSPF ASBR ABR ExtLSA ExtLSACsum OrigNewLSA RxNewLSA SpfHoldTime E NO YES 0 0x RouterId Selection: User Configured Export Static: Disabled Export Static: Disabled Export Rip: Disabled ASBR route Filter: None

90 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Laboratory Exercise OSPF Lab6 Utilizing the CLI Commands: l config ospf area normal l config ospf area stub l show ospf

91 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Lab6 - Network Topology

92 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration More OSPF Configuration Commands config ospf routeid config ospf area add range config ospf vlan area cost config ospf vlan area priority *enable iproute sharing enable/disable ospf exportstatic type config ospf vlan area virtual link authentication config ospf vlan area virtual link timer config ospf spf-hold-time show ospf lsdb

93 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf area add range config ospf area add range [advertise | noadvertise] {type 3|type 7} config ospf area delete range l Configures or deletes a range of IP addresses in an OSPF area. l On add, and if advertised, the range is exported as a single LSA by the ABR.

94 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf … cost config ospf [vlan | area | all] cost l Configures the cost (metric) of one or all interface(s). l The default cost of an interface is 1. l The maximum cost is 65,535.

95 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf … priority config ospf [vlan | area | all] priority l Configures the priority used in the designated router-election algorithm for one or all IP interface(s) or for all the interfaces within the area. l The range is l The Default priority setting is 1 l A value of 0 disqualifies the router from election

96 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - enable iproute sharing enable iproute sharing l Enables load sharing if multiple routes to the same destination are available (equal cost multipath) l Only paths with the same lowest cost are shared. The default setting is disabled.

97 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - enable/disable ospf exportstatic enable ospf export static cost { } [ase-type-1|ase-type-2] {tag } disable ospf export static l Enable/disables the distribution of static routes into the OSPF domain. l The default tag number is 0. l The default setting is disabled.

98 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf … authentication config ospf [vlan | area | virtual-link ] authentication [simple-password | md5 | none] l Configure OSPF authentication information for one interface or all the interfaces in an AREA. l When the OSPF AREA ID is specified, then the authentication information is applied to all the OSPF interfaces within the area.

99 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf … timer config ospf [vlan | area | virtual- link ] timer l Configures the timers for one interface or all the interfaces in the same OSPF area. l The following default, min, and max values (in seconds) are used: VariableDefaultMinMax RETRANSMISSION DELAY HELLO DEAD INTERVAL

100 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - config ospf spf-hold-time config ospf spf-hold-time { } l Configures the minimum number of seconds between Shortest Path First (SPF) recalculations. l The default setting is 3 seconds.

101 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration CLI Command - show ospf lsdb show ospf lsdb {detail} area [ | all] [router | network | summary-net | summary-asb | as_external | external-type 7 | all} l Displays a table of the current LSDB. l The user can filter the display using either area ID, the remote router's router ID, or the link state ID. Default is all with no detail. If detail is specified, each entry includes complete LSA information

102 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Example: show ospf lsdb OSPF_LAB_2:18 # show ospf lsdb area all all Router LSAs for area Link State ID Adv Router Seq# Age Chksum #Links x d xafc x x835f x800040a xf x x6e4c x800001ab x7f x c 461 0x Network LSAs for area Link State ID Adv Router Seq# Age Chksum x xb14f Summary LSAs for area Link State ID Adv Router Seq# Age Chksum x x dfc x b xd x x22f x xc698

103 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Laboratory Exercise OSPF Lab7

104 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Lab7 - Network Topology

105 LE Unicast Routing and L3 Switch Configuration Module OSPF Overview and Configuration Summary Define OSPF, features, advantages over RIP Describe OSPF LSA, format and Types Define LSDB, Initial synchronization, database exchange & reliable flooding Describe Routing Calculations, supported network type & Database Synchronization Describe how to build OSPF Networks Define the OSPF routing, areas, router types and virtual Links Differentiate DR, BDR, Router Election OSPF Configuration and Examples Lab Exercises


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