ospf

No Slide TitleLE-201 - Unicast Routing and L3 Switch Configuration Module 4 - * OSPF Overview and Configuration
Module 4
OSPF Overview and Configuration
LE-201 - Unicast Routing and L3 Switch Configuration Module 4 - * OSPF Overview and Configuration
Module Objectives
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
Summary
Define OSPF
More efficient than RIP
The OSPF Advantage
OSPF is an interior gateway protocol (IGP) that is more efficient than RIP.
Consumes fewer network resources
Route load sharing
Greater security
Link-state Protocol
Each router advertises a description of its local environment
interfaces
costs
Routing table is derived from this database
Utilize a shortest-path first algorithm
OSPF is a Link-state routing protocol
Basic Features of OSPF
Areas and Inter-area Routing
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
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.
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.
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.
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
LS Age
LS Type
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.
LS Age
LS Type
LSA Format - LS Type
Type 1
Type 2
Type 3
Type 4
Type 5
Type 7
LS Age
LS Type
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
LS Age
LS Type
LSA Format - Advertising Router
The originating router’s OSPF router ID
In practice, this is one of the router’s IP address
LS Age
LS Type
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.
LS Age
LS Type
LSA Format - LS Checksum
Does not include LS Age field
Derived using Fletcher checksum algorithm
LS Age
LS Type
LSA Types
4 Summary-LSAs (ASBR)
5 AS external-LSAs
7 NSSA external-LSAs
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
LS Age
LS Type
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
LS Age
LS Type
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
LS Age
LS Type
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
LS Age
LS Type
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
LS Age
LS Type
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
LS Age
LS Type
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
0
3
Sheet2
Sheet3
Router LSA Format - Link Data
For transit and Virtual Links
specifies the IP address of associated router interface.
For stub networks
0
Link 2, etc.
Router LSA Format - Metric
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.
0
Link 2, etc.
Link-State Database (LSDB)
Gives complete description of the network:
routers
interconnectivity (how it is interconnected)
LSDBs are exchanged between neighboring routers soon after routers discover each other
Maintained through a procedure called reliable flooding
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.
Switch A
Switch B
Synchronize Databases
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
Request the full LSA for new or newer headers
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.
Switch A
Switch F
switch b
switch c
switch d
switch e
Example LSDB Initial Synchronization
Database Description: Sequence = X
Database Description: Sequence = X with 6 LSA headers
(Router LSA, Switch A, 0x80000007) (Router LSA, Switch b, 0x800000b2) (Router LSA, Switch c, 0x80000003)
Database Description: Sequence = X+1 LSA header = (router LSA, switch F, 0x80000001)
Database Description: Sequence = X+1
Link State Request Packet for the following LSAs:
(Router LSA, Switch A) (Router LSA, Switch b) (Router LSA, Switch c)
(Router LSA, Switch d) (Router LSA, Switch e) (Router LSA, Switch F)
Bidirectionality established
Link State Update packet for the following LSAs:
(Router LSA, Switch A, 0x80000007) (Router LSA, Switch b, 0x800000b2) (Router LSA, Switch c, 0x80000003)
(Router LSA, Switch d, 0x80000021) (Router LSA, Switch e, 0x80000012) (Router LSA, Switch F, 0x80000005)
(Router LSA, Switch d, 0x80000021) (Router LSA, Switch e, 0x80000012) (Router LSA, Switch F, 0x80000005)
Database Exchange sequence number created
Link State Update packet, LSA = (router LSA, switch F, 0x80000006)
Sequence number incremented, acknowledges previous exchange pair
empty database description packet used for acknowledgement
Router requests all LSAs not in its local database
Updated LSA for switch F with larger sequence number
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
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.
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
Switch A
Switch B
Switch C
Switch D
Switch E
Switch F
Switch G
Switch H
Switch K
Switch J
Switch I
1
1
1
1
1
1
5
5
5
5
1
2
2
1
1
3
Candidate List Destination (cost, next hops)
Switch A (1, Switch A) Switch B (1, Switch B) Switch D (2, Switch D) Switch E (2, Switch E)
Switch C
Switch A
Switch B (1, Switch B) Switch D (2, Switch D) Switch E (2, Switch E)
Switch D (2, Switch D) Switch E (2, Switch E)
Switch B
4
Switch E (2, Switch E) Switch I (3, Switch D) Switch J (3, Switch D) Switch K (3, Switch D)
Switch E
5
Switch I (3, Switch D) Switch J (3, Switch D) Switch K (3, Switch D) Switch F (3, Switch E) Switch G (3, Switch E) Switch H (3, Switch E)
Switch I Switch J Switch K Switch F Switch G
Switch I
11
Shortest Path First Calculation for Switch "C"
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.
Switch A
Switch B
Switch C
Switch D
Switch E
Switch F
Switch G
Switch H
Switch K
Switch J
Switch I
1
1
1
1
1
1
5
5
5
5
1
2
2
1
1
3
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.
Switch A
Switch B
Switch C
Switch D
Switch E
Switch F
Switch G
Switch H
Switch K
Switch J
Switch I
5
1
1
1
5
1
3
3
3
5
1
2
4
1
5
3
OSPF Network Types
X.25, ATM
Point-to-Multipoint networks
Frame Relay
Broadcast networks
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)
10.1.1.1
10.1.1.5
10.1.1.3
10.1.1.4
10.1.1.2
OSPF Network Type - Broadcast Networks
Only network type supported by Extreme switches
Other Network Types are for WAN use
10.1.1.1
10.1.1.5
10.1.1.3
10.1.1.4
10.1.1.2
Broadcast Networks Terminology
DR - Designated Router
BDR - Backup DR
Network LSAs
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
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
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).
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
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
LS Age
Attached Router 2, etc.
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.
Designated Router-orginated network-LSA
router-LSA link-state ID
Router 1 router-LSA
Router 3 router-LSA
Router 4 router-LSA
Router 2 router-LSA
network-LSA link-state ID
Building OSPF Networks
CLI Commands for OSPF Configuration
Hierarchical Routing
Saves router memory consumed by the routing table
Saves router resources when computing the routing table
Saves link bandwidth when distributing routing data
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.
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.
Area A
Area B
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.
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.
g
10.5.1.0/24
10.5.2.0/24
10.5.3.0/24
10.5.4.0/24
Aggregate!!!
10.5.0.0/16
Types of OSPF Areas
Stub Areas
Not-So-Stubby-Areas (NSSA)
Virtual Links
Normal Area
Stub area
Support ASBRs
Can distribute external routes
Area 0 (Backbone)
Consist of
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
Stub Area
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
Not-So-Stubby-Area (NSSA)
Similar to existing OSPF Stub Area with two additional capabilities
External routes originating from ASBR connected to NSSA can be advertised within
External routes originating from NSSA can be propagated to other areas, including the backbone.
OSPF Defines Three types of Routers
Internal Router (IR)
Area Border Router (ABR)
Autonomous System Boundary Router (ASBR)
OSPF Hierarchical Components
ABR
ABR
ABR
ASBR
*All other routers that are not labeled ASBR or ABR are Internal Routers
Internet
Area 2
Area 1
Area 3
Autonomous System
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
OSPF Configuration Example
VL
VL
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
Do not use 0.0.0.0 as a router ID
OSPF CLI Commands
show ospf area
show ospf interfaces
CLI Command - enable/disable ospf
enable ospf
disable ospf
Enable or disable OSPF for the whole router. Default is disabled.
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.
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.
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).
CLI Command - show ospf
Displays global OSPF information.
show ospf area {<areaid>}
Displays information about a particular OSPF area, or all OSPF areas.
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
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
Interfaces:
IP addr Ospf State DR IP addr BDR IP addr
10.11.1.1 /24 E DR 10.11.1.1 10.11.1.2
Inter-Area route Filter: None
External route Filter: None
Configured Address Ranges:
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.
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:
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
Laboratory Exercise
Lab4 - OSPF Configuration I
Lab4 - Network Topology
Normal 10.13.0.0 NORM131 10.13.1.0/24
Normal 10.11.0.0 NORM111 10.11.1.0/24
More OSPF Configuration
show ospf virtual-link
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).
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
Link state, DR ID, BDR ID, and dead time
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
AreaId: 10.15.0.0 NbrRouterId: 30.30.30.30
Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40
Auth Type: NONE
Laboratory Exercise
Lab5 - OSPF Configuration II
Lab5 - Network Topology 1
Backbone 0.0.0.0 BBONE1 10.0.1.0/24
Network
Physical
Lab5 - Network Topology 2
Backbone 0.0.0.0 BBONE1 10.0.1.0/24
Network
Physical
More OSPF Configuration - Areas
config ospf area normal
config ospf area stub
config ospf area nssa
show ospf
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
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
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.
CLI Command - show ospf
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
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
Laboratory Exercise
OSPF Lab6
show ospf
.2
.1
.2
.1
.3
.2
.1
Port1 x-over to Port2
More OSPF Configuration Commands
*enable iproute sharing
config ospf spf-hold-time
show ospf lsdb
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.
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.
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
CLI Command - enable iproute sharing
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.
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.
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.
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
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.
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
Example: show ospf lsdb
Router LSAs for area 0.0.0.0
Link State ID Adv Router Seq# Age Chksum #Links
-------------------------------------------------------------
Network LSAs for area 0.0.0.0
Link State ID Adv Router Seq# Age Chksum
-------------------------------------------------------------
Link State ID Adv Router Seq# Age Chksum
-------------------------------------------------------------
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
Laboratory Exercise
OSPF Lab7
OSPF_LAB_6
OSPF_LAB_4
OSPF_LAB_1
OSPF_LAB_5
OSPF_LAB_3
OSPF_LAB_2
.2
.1
.2
.1
.3
.2
.1
Summarize to 10.15.0.0/16
Summarize to 10.21.0.0/16
.1
.3
.2
Summary
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
Iteration
Switch C1
2Switch A
Switch B3
Switch D4
Switch E5
Switch I
Switch J
Switch K
Switch F
Switch G
Switch IEmpty
LS Age
Designated Router
4Virtual linkNeighbor Router ID
A
LSA header = (router LSA, switch F, 0x80000001)
Database Description: Sequence = X+1
Link State Request Packet for the following LSAs:
(Router LSA, Switch A)
(Router LSA, Switch b)
(Router LSA, Switch c)
(Router LSA, Switch d)
(Router LSA, Switch e)
(Router LSA, Switch F)
(Router LSA, Switch A, 0x80000007)
(Router LSA, Switch b, 0x800000b2)
(Router LSA, Switch c, 0x80000003)
(Router LSA, Switch d, 0x80000021)
(Router LSA, Switch e, 0x80000012)
(Router LSA, Switch F, 0x80000005)
Link State Update packet for the following LSAs:
(Router LSA, Switch A, 0x80000007)
(Router LSA, Switch b, 0x800000b2)
(Router LSA, Switch c, 0x80000003)
(Router LSA, Switch d, 0x80000021)
(Router LSA, Switch e, 0x80000012)
(Router LSA, Switch F, 0x80000005)
Link State Update packet, LSA =
(router LSA, switch F, 0x80000006)
Bidirectionality established
exchange pair
acknowledgement
10.1.1.1 10.1.1.510.1.1.3
Port1 x-over to Port2 Port1 x-over to Port2
Port1 x-over to Port2 Port1 x-over to Port2
Port 17

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