Module 4 OSPF Overview and Configuration LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Define OSPF Dynamic Routing Protocol Link State Protocol Employ a distributed database model More efficient than RIP LE-201 - STUDENT GUIDE Rev1.2_Oct99

The OSPF Advantage OSPF is an interior gateway protocol (IGP) that is more efficient than RIP. Consumes fewer network resources Highly scalable Faster convergence A more descriptive routing metric Route load sharing Greater security LE-201 - STUDENT GUIDE Rev1.2_Oct99

Link-state Protocol Employ a distributed database model. Each router advertises a description of its local environment interfaces costs neighbor information Uses a single synchronized database for collecting advertisements (LSDB) Routing table is derived from this database Utilize a shortest-path first algorithm OSPF is a Link-state routing protocol LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Hello Packet & Neighbor Discover 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 Hello packets are sent out every 10 seconds by default If subsequent Hello packet is not received within 40 seconds, neighbor relationship is terminated LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Hello Packets Will only be recognized by routers attached to the same subnet with same subnet mask Contains information on parameters for Hello Interval and 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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 NOTE: An OSPF router will not forward data packets over a unidirectional link. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Format - LS Age Number of seconds since the LSA was originated normally 0 - 30 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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Format - LS Type Classifies the LSA according to function Type 1 LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Format - Link State ID A unique identification Used to describe a router in the OSPF routing domain Depends on the LS Type Type 1, 2, 3, 4, 5 or 7 LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Format - Advertising Router The originating router’s OSPF router ID In practice, this is one of the router’s IP address LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Format - LS Checksum Used to detect data corruption. Does not include LS Age field Derived using Fletcher checksum algorithm LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSA Types Type Number Description 1 Router-LSAs 2 Network-LSAs 3 Summary-LSAs (IP network) 4 Summary-LSAs (ASBR) 5 AS external-LSAs 7 NSSA external-LSAs LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

LS Type 3 - Summary-LSAs (IP Network) This originate from Area Border Routers (ABRs) Supports hierarchical routing through the use of OSPF areas Link State ID field is an IP network number LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Router LSA Format - Link ID Originating router’s link information follows the LSA header. There are four Link IDs determined by Link Type. Type 1 Neighboring router’s Router ID Three of this Link ID are relevant in a broadcast network LE-201 - STUDENT GUIDE Rev1.2_Oct99

Router LSA Format - Link Data For transit and Virtual Links specifies the IP address of associated router interface. For stub networks Specifies the stub network mask LE-201 - STUDENT GUIDE Rev1.2_Oct99

Router LSA Format - Metric The cost of using this router link. A user-configurable value from 1 - 65,535 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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Link-State Database (LSDB) The collection of all OSPF LSAs received Each OSPF router has an identical LSDB Gives complete description of the network: routers network segments interconnectivity (how it is interconnected) LSDBs are exchanged between neighboring routers soon after routers discover each other Maintained through a procedure called reliable flooding LE-201 - STUDENT GUIDE Rev1.2_Oct99

LSDB Initial Synchronization When two neighbors first start communicating, they must synchronize their databases before forwarding traffic over their shared link to prevent routing loops from occurring. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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: Forward current LSA headers Compares the header received to the LSDB Request the full LSA for new or newer headers LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example LSDB Initial Synchronization LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Database - Reliable Flooding LSA Updates are periodically generated by a router wishing to update a self-originated LSA because: The router’s local state may have changed The router wants to delete one of its self-originated LSAs Used to propagate LSA Updates throughout the routing domain LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Routing Calculations With router LSDBs synchronized for all routers in routing domain The router will use Dijkstra’s Shortest Path First algorithm This allows calculation of shortest paths to all destinations Routing table is constructed from the calculations and includes network destinations associated costs LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Routing Calculations Every link carries an associated cost. LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Routing Calculations LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Network Types Point-to-Point networks Serial lines Non-broadcast Multi-access (NBMA) networks X.25, ATM Point-to-Multipoint networks Frame Relay Broadcast networks LE-201 - STUDENT GUIDE Rev1.2_Oct99

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) LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Network Type - Broadcast Networks Only network type supported by Extreme switches Other Network Types are for WAN use LE-201 - STUDENT GUIDE Rev1.2_Oct99

Broadcast Networks Terminology DR - Designated Router BDR - Backup DR DR and BDR Election Network LSAs LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. 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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Database Synchronization An OSPF router will send its Link State Update (LSU) to the DR and BDR The destination IP address for the LSU will be multicast address 224.0.0.6 (All DRouters). The DR will then flood the update to all OSPF routers The destination IP address for the LSU will be multicast address 224.0.0.5 (All OSPFRouters). LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. 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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Building OSPF Networks Hierarchical Routing OSPF Routing Hierarchy OSPF Areas OSPF Types of Routers Virtual Links CLI Commands for OSPF Configuration LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Areas Defined The OSPF hierarchy is maintained through the deployment of OSPF areas 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 These LSAs describe area’s topology Routing with an area is flat. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 Condense the topological information of their attached areas into Type 3: Summary-LSAs for distribution to the backbone. The backbone in turn distributes the information to the other areas. LE-201 - STUDENT GUIDE Rev1.2_Oct99

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. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Types of OSPF Areas Normal Area Stub Areas Not-So-Stubby-Areas (NSSA) Area 0 (Backbone) Stub Areas Not-So-Stubby-Areas (NSSA) Virtual Links LE-201 - STUDENT GUIDE Rev1.2_Oct99

Normal Area An area which is not a: Stub area NSSA Can be placed anywhere within the OSPF routing domain Support ASBRs Support Virtual Links Can distribute external routes LE-201 - STUDENT GUIDE Rev1.2_Oct99

Area 0 (Backbone) Is a Normal Area Responsible for distributing routing information between areas Consist of all area border routers networks not contained in any other area and their attached routers Has an Area ID of 0.0.0.0 Only one backbone area per AS All areas are required to attach directly to the OSPF backbone area LE-201 - STUDENT GUIDE Rev1.2_Oct99

Stub Area For routers with limited resources reduce memory and computation requirements The LSDB is kept as small as possible External route information is not distributed 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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Not-So-Stubby-Area (NSSA) Similar to existing OSPF Stub Area with two additional capabilities External routes originating from ASBR connect- ed to NSSA can be advertised within External routes originating from NSSA can be propagated to other areas, including the backbone. LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Defines Three types of Routers Internal Router (IR) Has all of its interfaces within the same area Area Border Router (ABR) Autonomous System Boundary Router (ASBR) LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Hierarchical Components OSPF Router Types Displayed Internet ABR ABR ASBR ABR *All other routers that are not labeled ASBR or ABR are Internal Routers LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

OSPF Configuration Example LE-201 - STUDENT GUIDE Rev1.2_Oct99

Configuring OSPF Must have a unique router ID for each switch Recommend manually setting the router ID of the switches participating in OSPF Simplifies router management Prevents corruption of virtual links Do not use 0.0.0.0 as a router ID LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - enable/disable ospf enable ospf disable ospf Enable or disable OSPF for the whole router. Default is disabled. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf add/del vlan config ospf add vlan [<name> | all] config ospf delete vlan [<name> | all] Enables or disables OSPF on one or all VLANs (router interfaces). The default setting is disabled. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - create/del ospf area create ospf area <areaid> delete ospf area [<areaid> | all] Create or delete an OSPF area. Area 0.0.0.0 does not need to be created. It exists by default. It also cannot be deleted. Once an OSPF area is removed, the associated OSPF area and OSPF interface information will also be removed. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf vlan area config ospf vlan <name> area <areaid> 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. By default, all router interfaces are associated with area 0.0.0.0 (backbone). LE-201 - STUDENT GUIDE Rev1.2_Oct99

show ospf area {<areaid>} CLI Command - show ospf show ospf Displays global OSPF information. show ospf area {<areaid>} Displays information about a particular OSPF area, or all OSPF areas. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example: show ospf area OSPF_Switch4: show ospf area Area: 0.0.0.0 Stub: FALSE Rtr Id: 20.20.20.20 Spf Runs: 48 Num ABR: 6 Num ASBR: 0 Num LSA: 43 LSA Chksum:0x170863 Interfaces: IP addr Ospf State DR IP addr BDR IP addr 10.0.2.1 /24 E DOWN 0.0.0.0 0.0.0.0 10.0.1.1 /24 E BDR 10.0.1.2 10.0.1.1 Inter-Area route Filter: None External route Filter: None Configured Address Ranges: Area: 10.11.0.0 Stub: FALSE Rtr Id: 20.20.20.20 Spf Runs: 21 Num ABR: 2 Num ASBR: 0 Num LSA: 35 LSA Chksum:0x16c3de 10.11.1.1 /24 E DR 10.11.1.1 10.11.1.2 LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - show ospf interfaces show ospf interfaces {vlan <name> | area <areaid>|all} Displays information about one or all OSPF area, or all OSPF areas. LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example: show ospf interface Summit4: sh ospf interface Interface(rif4): 10.15.1.1/24 Vlan: norm151 Ospf: ENABLED Router: ENABLED AreaId: 10.15.0.0 RtId: 20.20.20.20 Cost: 1 Pri: 1 Transit Delay: 1 Hello Interval: 10s Rtr Dead Time: 40s Retransmit Interval: 5s Authentication: NONE State: BDR Number of events: 1 DR RtId: 30.30.30.30 DR IP addr: 10.15.1.3 BDR IP addr: 10.15.1.1 Neighbours: RtrId: 10.10.10.10 IpAddr: 10.15.1.2 Pri: 1 State: FULL Dr: 10.15.1.3 BDR: 10.15.1.1 Dead Time: 7 RtrId: 30.30.30.30 IpAddr: 10.15.1.3 Pri: 1 State: FULL Dr: 10.15.1.3 BDR: 10.15.1.1 Dead Time: 6 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Laboratory Exercise Lab4 - OSPF Configuration I LE-201 - STUDENT GUIDE Rev1.2_Oct99

Lab4 - Network Topology LE-201 - STUDENT GUIDE Rev1.2_Oct99

More OSPF Configuration config ospf add virtual-link config ospf delete virtual-link show ospf virtual-link LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf add virtual-link config ospf add virtual-link <routerid> <areaid> config ospf delete virtual-link <routerid> <areaid> Adds or deletes a virtual link connected to another area border router (ABR). Specify the following: routerid -- Far-end router ID. Areaid -- Transit area used for connecting the two end-points. The transit area cannot be the backbone (0.0.0.0). LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - show ospf virtual-link show ospf virtual-link {<areaid><routerid> | all} Displays virtual link information about a particular router or all routers. Default is all. Contains: Area ID and neighbor router ID Receive interval, transit delay, Hello interval, and dead interval. Authentication configuration Virtual link type and number of events Neighbor router ID, IP address, and priority Link state, DR ID, BDR ID, and dead time LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example: show ospf virtual-link OSPF_LAB_2:19 # show ospf virtual-link AreaId: 10.15.0.0 NbrRouterId: 10.10.10.10 Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40 Auth Type: NONE State: P2P Number of Events: 3 RtrId: 10.10.10.10 IpAddr: 10.15.1.2 Pri: 1 State: FULL Dr: 0.0.0.0 BDR: 0.0.0.0 Dead Time: 9 AreaId: 10.15.0.0 NbrRouterId: 30.30.30.30 State: P2P Number of Events: 1 RtrId: 30.30.30.30 IpAddr: 10.15.1.3 Pri: 1 State: FULL Dr: 0.0.0.0 BDR: 0.0.0.0 Dead Time: 7 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Laboratory Exercise Lab5 - OSPF Configuration II LE-201 - STUDENT GUIDE Rev1.2_Oct99

Lab5 - Network Topology 1 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Lab5 - Network Topology 2 LE-201 - STUDENT GUIDE Rev1.2_Oct99

More OSPF Configuration - Areas config ospf area normal config ospf area stub config ospf area nssa show ospf LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf area normal config ospf area <areaid> normal Configure an OSPF area as a normal area Default area type is normal Area 0.0.0.0 can only be normal LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf area stub config ospf area <areaid> stub [summary|nosummary] stub-default-cost <cost> Configures an OSPF area as a stub area. Stub-default-cost is the the cost of the default summary-LSA that the router should advertise into the area LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf area nssa config ospf area <areaid> nssa [summary|nosummary] stub-default-cost <cost> {translate} Configures an OSPF area as a NSSA. Stub-default-cost is the the cost of the default summary-LSA that the router should advertise into the area Translate option: determines whether type 7 LSAs are translated into type 5 LSAs. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - show ospf show ospf Display global OSPF information: Router ID OSPF state Is router an autonomous system boundary router (Y/N)? Is router an area border router (Y/N)? Number of external LSAs processed External LSA checksum Number of originating new LSAs Number of received new LSAs Shortest Path First hold time LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example: show ospf Summit4: show ospf Router Id OSPF ASBR ABR ExtLSA ExtLSACsum OrigNewLSA RxNewLSA SpfHoldTime 20.20.20.20 E NO YES 0 0x0 14694 20634 3 RouterId Selection: User Configured Export Static: Disabled Export Static: Disabled Export Rip: Disabled ASBR route Filter: None LE-201 - STUDENT GUIDE Rev1.2_Oct99

Laboratory Exercise OSPF Lab6 Utilizing the CLI Commands: config ospf area normal config ospf area stub show ospf LE-201 - STUDENT GUIDE Rev1.2_Oct99

Lab6 - Network Topology LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf area add range config ospf area <areaid> add range <ipaddress> <mask> [advertise | noadvertise] {type 3|type 7} config ospf area <areaid> delete range <ipaddress> <mask> Configures or deletes a range of IP addresses in an OSPF area. On add, and if advertised, the range is exported as a single LSA by the ABR. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf … cost config ospf [vlan <name> | area <areaid> | all] cost <number> Configures the cost (metric) of one or all interface(s). The default cost of an interface is 1. The maximum cost is 65,535. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf … priority config ospf [vlan <name> | area <areaid> | all] priority <number> 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. The range is 0 - 255 The Default priority setting is 1 A value of 0 disqualifies the router from election LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - enable iproute sharing Enables load sharing if multiple routes to the same destination are available (equal cost multipath) Only paths with the same lowest cost are shared. The default setting is disabled. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - enable/disable ospf exportstatic enable ospf export static cost {<metric>} [ase-type-1|ase-type-2] {tag <number>} disable ospf export static Enable/disables the distribution of static routes into the OSPF domain. The default tag number is 0. The default setting is disabled. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf … authentication config ospf [vlan <name> | area <areaid> | virtual-link <routerid> <areaid>] authentication [simple-password <password> | md5 <md5_key_id> <md5_key> | none] Configure OSPF authentication information for one interface or all the interfaces in an AREA. When the OSPF AREA ID is specified, then the authentication information is applied to all the OSPF interfaces within the area. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf … timer config ospf [vlan <name> | area <areaid> | virtual-link <routerid>] timer <retransmission_interval> <transmission_delay> <hello_interval> <dead_interval> Configures the timers for one interface or all the interfaces in the same OSPF area. The following default, min, and max values (in seconds) are used: Variable Default Min Max RETRANSMISSION 5 0 3600 DELAY 1 0 3600 HELLO 10 1 65535 DEAD INTERVAL 40 1 2147483647 LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - config ospf spf-hold-time config ospf spf-hold-time {<seconds>} Configures the minimum number of seconds between Shortest Path First (SPF) recalculations. The default setting is 3 seconds. LE-201 - STUDENT GUIDE Rev1.2_Oct99

CLI Command - show ospf lsdb show ospf lsdb {detail} area [<areaid> | all] [router | network | summary-net | summary-asb | as_external | external-type 7 | all} Displays a table of the current LSDB. 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 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Example: show ospf lsdb OSPF_LAB_2:18 # show ospf lsdb area all all Router LSAs for area 0.0.0.0 Link State ID Adv Router Seq# Age Chksum #Links ------------------------------------------------------------- 10.10.10.10 10.10.10.10 0x8000011d 1227 0xafc6 1 20.20.20.20 20.20.20.20 0x80006754 510 0x835f 3 30.30.30.30 30.30.30.30 0x800040a9 1245 0xf018 1 40.40.40.40 40.40.40.40 0x80000169 450 0x6e4c 1 50.50.50.50 50.50.50.50 0x800001ab 1279 0x7f83 3 60.60.60.60 60.60.60.60 0x8000016c 461 0x8095 1 Network LSAs for area 0.0.0.0 Link State ID Adv Router Seq# Age Chksum 10.0.1.2 50.50.50.50 0x80000169 1273 0xb14f Summary LSAs for area 0.0.0.0 10.11.1.0 10.10.10.10 0x80000114 1230 0x dfc 10.11.1.0 20.20.20.20 0x8000011b 1250 0xd109 10.12.0.0 10.10.10.10 0x80000109 1018 0x22f2 10.13.1.0 20.20.20.20 0x80000194 1250 0xc698 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Laboratory Exercise OSPF Lab7 LE-201 - STUDENT GUIDE Rev1.2_Oct99

Lab7 - Network Topology LE-201 - STUDENT GUIDE Rev1.2_Oct99

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 LE-201 - STUDENT GUIDE Rev1.2_Oct99