Plz Note : Some Topics That You Might Want To Pursue On Your Own That We Did Not Cover In This Article Are Listed Here. This Page Discusses “ OSPF CONFIGURATION TROUBLESHOOTING COMMAND REFERENCES FOR CISCO IOS”, And Also We Request To The Students, Please Go Through All The Articles That Are We Posted In This Web Site And Identify All The CISCO IOS Commands In The Lab Practice Before Going To Access This Page. Thank You!
FOR MORE OSPF REFERENCES:
1. ◙ - ➤ Protocol Comparison OSPF, EIGRP, BGP And RIP:
2. ◙ - ➤ OSPFv2 (IPv4) Vs OSPFv3 (IPv6)
3. ◙ - ➤ OSPF Quick Reference:
4. ◙ - ➤ OSPF Quick IOS Commands Reference Table:
5. ◙ - ➤ Short Notes Of OSPF:
6. ◙ - ➤ OSPF LSA Operation And It’s Types:
7. ◙ - ➤ OSPF Configuration Examples:
8. ◙ - ➤ OSPF MD5:
9. ◙ - ➤ Redistribution OSPF Vs EIGRP:
10. ◙ - ➤ OSPF Review Questions And Answers:
11. ◙ - ➤ Just Recap About OSPF With Quest:
12. ◙ - ➤ IPv6 OSPF VIRTUAL-LINK:
13. ◙ - ➤ OSPF Interface Configuration Command References:
TROUBLESHOOTING OSPF COMMANDS:
Router(Config-Router)#Network 172.16.0.0 0.0.255.255 Area 0 - > OSPF Advertises Interfaces, Not Networks. Uses The Wildcard Mask To Determine Which Interfaces To Advertise.
Router(Config-If)#IP OSPF Hellointerval Timer 20 - > Changes The Hello Interval Timer To 20 Seconds.
Router(Config-If)#IP OSPF Deadinterval 80 - > Changes The Dead Interval Timer To 80 Seconds.
Note: Hello And Dead Interval Timers Must Match For Routers To Become Neighbors.
Router#Clear IP Route * - > Clears Entire Routing Table, Forcing It To Rebuild.
Router#Clear IP Route A.B.C.D - > Clears Specific Route To Network A.B.C.D
Router#Clear IP OPSF Counters - > Resets OSPF Counters.
Router#Clear IP OSPF Process - > Resets Entire OSPF Process, Forcing OSPF To Re-Create Neighbors, Database, And Routing Table.
Router#Show IP Protocol - > Displays Parameters For All Protocols Running On The Router.
Router#Show IP Route - > Displays A Complete IP Routing Table.
Router#Show IP OSPF - > Displays Basic Information About OSPF Routing Processes.
Router#Show IP OSPF Interface - > Displays OSPF Info As It Relates To All Interfaces.
Router#Show IP OSPF Interface Fastethernet 0/0 - > Displays OSPF Information For Interface Fastethernet 0/0.
Router#Show IP OSPF Border-Routers - > Displays Border And Boundary Router Information.
Router#Show IP OSPF Neighbor - > Lists All OSPF Neighbors And Their States.
Router#Show IP OSPF Neighbor Detail - > Displays A Detailed List Of Neighbors.
Router#Debug IP OSPF Events - > Displays All OSPF Events.
Router#Debug IP OSPF Adjacency - > Displays Various OSPF States And DR/ BDR Election Between Adjacent Routers.
Router#Debug IP OSPF Packets - > Displays OPSF Packets.
TROUBLESHOOTING OSPF SHOW COMMANDS: SHOW IP PROTOCOLS: It Displays OSPF Status, Process-ID And Neighbors/Gateways. It Also Shows Area Types Configured (Normal, Stub, NSSA Etc).
SHOW IP OSPF INTERFACES: Displays OSPF Interfaces. It Also Shows Type(S) Of Network, Neighbor Count, Type Of Authentication And Timer Values.
SHOW IP OSPF NEIGHBORS: Displays Active Fully Adjacent Neighbors, Router ID Of Neighbors, Neighbor State/DR State, IP Addresses/Interfaces And Dead Time Of Neighbors.
SHOW IP ROUTE OSPF: Displays OSPF Routes That Are Being Received From Neighbors And Their Administrative Distances. It Also Shows The Cumulative Cost Metric To Reach A Particular Subnet And What The Route Source And Interface Is.
SHOW IP OSPF: Displays OSPF Process ID, Configured Areas, Number Or Types Of Areas, It Also Shows The Number Of Times The SPF Algorithm Is Executed. If You See A Very High Number Of SPF Calculations, It Could Be A Flapping Router Or An Interface With An Issue.
SHOW IP OSPF DATABASE: Displays LSA Types Per Area, Advertising Router, Link ID (Subnet) And Age.
SHOW IP OSPF BORDER-ROUTERS: Displays Router ID, Advertising Router, Area, ABR Or ASBR, And Cost Details.
TROUBLESHOOTING OSPF DEBUG COMMANDS: DEBUG IP OSPF ADJACENCY: It Is Used To Debug Neighbor Adjacencies.
DEBUG IP OSPF EVENTS: It Is Used To Debug Network Events. Neighbor Relationships, Routing Update Issues And Stub Router Problems.
DEBUG IP SPF HELLO: It Is Used To Debug Neighbor Adjacencies. Routing Update Issues, Convergence Issues And Interface Flapping And Neighbor Relationships, Configuration Issues And DR/BDR Election Problems.
REQUIRED AND OPTIONAL OSPF CONFIGURATION COMMANDS
Router(Config-Router)#Network Address Wildcard-Mask Area Area-ID
OPTIONAL OSPF CONFIGURATION COMMANDS – REVIEW: Router(Config-Router)# Default-Information Originate - > (Send Default).
Router(Config-Router)# Area Area Authentication - > (Plain Authentication).
Router(Config-Router)# Area Area Authentication Message-Digest - > (MD5 Authentication).
Router(Config)# Interface Loopback Number - > (Configure Loopback As Router ID).
Router(Config)# Interface Type Slot/Port
Router(Config-If)# IP OSPF Priority <0-255> - > (DR/BDR Election).
Router(Config-If)# Bandwidth Kbps - > (Modify Default Bandwdth).
Router(Config-If)# IP OSPF Cost Cost - > (Modify Inter. Cost).
Router(Config-If)# IP OSPF Hello-Interval Seconds - > (Modify Hello).
Router(Config-If)# IP OSPF Dead-Interval Seconds - > (Modify Dead).
Router(Config-If)# IP OSPF Authentication-Key Passwd - > (Plain/MD5 Authentication).
RouterConfig-If)# IP OSPF Message-Digest-Key Key-ID MD5 Password
ENABLING OSPF
But This Is Not True Of Enhanced Interior Gateway Routing Protocol [EIGRP], In Which The Routers Need To Be In The Same Autonomous System. Cisco IOS® Software Can Run Multiple OSPF Processes On The Same Router, And The Process ID Merely Distinguishes One Process From The Another. The Process ID Should Be A Positive Integer. In This Example, The Process ID Is 1.
OSPF ROUTER ID: The OSPF Router ID Is Used To Uniquely Identify Each Router In The OSPF Routing Domain. It's Simply An IP Address. It's Derived Based On Three Criteria With The Following Precedence: The OSPF Router ID Is A 32−Bit IP Address Selected At The Start Of The OSPF Process. The Highest IP Address Configured On The Router Is The Router ID. If A Loopback Address Is Configured, It Is The Router ID. In The Case Of Multiple Loopback Addresses, The Highest Loopback Address Is The Router ID. Once The Router ID Is Elected, It Does Not Change Unless OSPF Restarts Or Is Manually Changed With The Router−ID 32−Bit−IP−Address Command Under Router OSPF Process−ID.
◙ The Router ID Can Be Manually Specified. Use The IP Address Configured With ODPF Router-ID Command.
◙ If Router-ID Is Not Configured, The Router Chooses The Higest IP Address Of Any Of Its Loopback Interfaces. It Is More Common To Find Routers Configured With A Loopback Interface Because Older Routers Do Not Have The Router-Id Command Available.
◙ If No Loopback Interfaces Are Configured, The Router Chooses The Highest IP Address Of Any Of Its Physical Interfaces. This Does Not Have To Be An OSPF-Enabled Interface, But It Must Be In The Up State.
The Router ID Is Showed Under The “Show IP Protocols” Command. The Router ID Must Be Unique, Otherwise, Chaos Will Reign. It's Kinda Like Dividing By 0.
ENABLING OSPF: ROUTER(CONFIG)# ROUTER OSPF PROCESS-ID
◙ PROCESS-ID: 1 - 65,535
◙ Cisco Feature, Which Allows You To Run Multiple, Different OSPF Routing Processes On The Same Router. (But Don’t!)
◙ Process-ID Is Locally Significant, And Does Not Have To Be The Same Number On Other Routers (They Don’t Care).
◙ This Is Different Than The Process-ID Used For IGRP And EIGRP Which Must Be The Same On All Routers Sharing Routing Information.
FYI - Cisco IOS Limits The Number Of Dynamic Routing Processes To 30. This Is Because It Limits The Number Of Protocol Descriptors To 32, Using One For Connected Route Sources, One For Static Route Sources, And 30 For Dynamic Route Sources.
CONFIGURING NETWORK COMMAND AND THE WILDCARD MASK: Router(Config)# Router OSPF Process-ID
Router(Config-Router)#Network Address Wildcard-Mask Area Area-ID
◙ Tells OSPF Which Interfaces To Enable OSPF On (Send And Receive Updates), Matching The Address And Wildcard Mask.
◙ Also, Tells OSPF To Include This Network In Its Routing Updates
◙ Wildcard Is Necessary Because OSPF Supports CIDR And VLSM
◙ Most Of The Time You Can Just Use An Inverse-Mask (Like Access-Lists) As The Network Wildcard Mask.
Router(Config-If)#IP Add 20.10.5.1 255.255.255.0
Router(Config)# Router OSPF 10
Router(Config-Router)#Network 20.10.5.0 0.0.0.255 Area 0
EXAMPLE FOR THE NETWORK WILDCARD MASK ON ROUTER R1: Router R1(Config)#Router OSPF 1
Router R1(Config-Router)#Network 192.168.1.0 0.0.0.255 Area 0
Router R1(Config-Router)#Network 192.168.2.0 0.0.0.255 Area 0
Router R1(Config-Router)#Network 192.168.20.0 0.0.0.3 Area 0
EXAMPLE FOR THE NETWORK WILDCARD MASK ON ROUTER R2: Router R2(Config)#Router OSPF 10
Router R2(Config-Router)#Network 192.168.20.0 0.0.0.3 Area 0
Router R2(Config-Router)#Network 192.168.30.0 0.0.0.255 Area 0
CONFIGURING THE OSPF ROUTING PROCESS: COST: This Is An OSPF Metric. Cost Is Calculated With This Formula:
Use The IP OSPF Cost Interface Cost Interface Configuration Command To Explicitly Specify The Cost On An Interface.
BANDWIDTH COMMAND:
Router(Config-If)# Bandwidth Kilobits
(Ex: 64 = 64,000bps)
◙ Changes The Default Bandwidth Metric On A Specific Interface.
◙ Used In The 108/Bandwidth Calculation For Cumulating The Cost Of A Route From The Router To The Network On The Outgoing Interfaces.
◙ Does Not Modify The Actual Speed Of The Link.
IP OSPF COST COMMAND: Router(Config-If)# IP OSPF Cost Value
(Ex: 1562, Same As Bandwidth = 64kbps)
◙ Configures The Cost Metric For A Specific Interface
◙ Uses This Value For The Cost Of This Interface Instead Of The 108/Bandwidth Calculation
◙ Common For Multivendor Environments.
CONFIGURING SIMPLE AUTHENTICATION: A Router, By Default, Trusts That Routing Information Received, Has Come From A Router That Should Be Sending It.
Router(Config-If)# IP OSPF Authentication-Key Passwd
◙ Configured On An Interface
◙ Password = Clear Text Unless Message-Digest Is Used (Next)
– Easily Captured Using A Packet Sniffer
– Passwords Do Not Have To Be The Same Throughout An Area, But They Must Be Same Between Neighbors.
AFTER A PASSWORD IS CONFIGURED, YOU ENABLE AUTHENTICATION FOR THE AREA ON ALL PARTICIPATING AREA ROUTERS WITH: Router(Config-Router)# Area Area Authentication
◙ Configured For An OSPF Area, In OSPF Router Mode.
EXAMPLE ON ROUTER A: Interface Serial 1
IP Address 192.16.64.1 255.255.255.0
IP OSPF Authentication-Key Secret
!
Router OSPF 10
Network 192.16.64.0 0.0.0.255 Area 0
Network 70.0.0.0 0.255.255.255 Area 0
Area 0 Authentication
EXAMPLE ON ROUTER B: Interface Serial 2
IP Address 192.16.64.2 255.255.255.0
IP OSPF Authentication-Key Secret
!
Router OSPF 10
Network 172.16.0.0 0.0.255.255 Area 0
Network 192.16.64.0 0.0.0.255 Area 0
Area 0 Authentication
CONFIGURING MD5 ENCRYPTED AUTHENTICATION (MD5 ENCRYPTION): Router(Config-If)# IP OSPF Message-Digest-Key Key-ID MD5 Password
◙ Key-ID = 1 To 255, Must Match On Each Router To Authenticate.
◙ MD5 = Encryption-Type
◙ Password = Encrypted
– Passwords Do Not Have To Be The Same Throughout An Area, But They Must Be Same Between Neighbors.
After A Password Is Configured, You Enable Authentication For The Area On All Participating Area Routers With: Router(Config-Router)# Area Area Authentication [Message-Digest]
◙ Message-Digest Option Must Be Used If Using Message-Digest-Key
◙ If Optional Message-Digest Is Used, A Message Digest, Or Hash, Of The Password Is Sent.
SET PASSWORD FOR OSPF MD5 AUTHENTICATION. IP OSPF Message-Digest-Key
The No Form Of The Command Removes The Password.
EXAMPLE: Router(Config)#Interface Ethernet Eth0
Router(Config-If Eth0)#IP OSPF Message-Digest-Key 22 MD5 Mysecret
Router(Config-If Eth0)#
EXAMPLE ON ROUTER A: Interface Serial1
IP Address 192.16.64.1 255.255.255.0
IP OSPF Message-Digest-Key 1 MD5 Secret
!
Router OSPF 10
Network 192.16.64.0 0.0.0.255 Area 0 Network 70.0.0.0 0.255.255.255 Area 0
Area 0 Authentication Message-Digest
EXAMPLE ON ROUTER B: Interface Serial2
IP Address 192.16.64.2 255.255.255.0
IP OSPF Message-Digest-Key 1 MD5 Secret
! Router OSPF 10
Network 172.16.0.0 0.0.255.255 Area 0
Network 192.16.64.0 0.0.0.255 Area 0
Area 0 Authentication Message-Digest
DEFAULT-INFORMATION ORIGINATE COMMANDS - PROPAGATING DEFAULT ROUTES IN AN OSPF DOMAIN: Router(Config)# IP Route 0.0.0.0 0.0.0.0 Serial0
Router(Config)# Router OSPF 1
Router(Config-Router)# Default-Information Originate [Always]
◙ If The ASBR Has A Default Route Configured (IP Route 0.0.0.0 0.0.0.0), The DEFAULT-INFORMATION ORIGINATE Command Is Necessary To Advertise 0.0.0.0/0 To The Other Routers In The Area.
◙ If The Default-Information Originate Command Is Not Used, The Default “Quad-Zero” Route Will Not Be Propagated.
◙ IMPORTANT: The Default Route And The DEFAULT-INFORMATION ORIGINATE Command Are Usually Only Be Configured On Your “Entrance” Or “Gateway” Router, The Router That Connects Your Network To The Outside World.
– This Router Is Known As The ASBR (Autonomous System Boundary Router)
◙ EXTRA: The Always Option Will Propagate A Default “Quad-Zero” Route Even If One Is Not Configured On This Router.
ENGINEERING AND MARKETING WILL HAVE 0.0.0.0/0 DEFAULT ROUTES FORWARDING PACKETS TO THE ENTRANCE ROUTER.
Entrance(Config)# IP Route 0.0.0.0 0.0.0.0 Serial 0
Entrance(Config)# Router OSPF 1
Entrance(Config-Router)# Network 10.0.0.0 0.0.0.255 Area 0
Entrance(Config-Router)# Network 11.0.0.0 0.0.0.255 Area 0
Entrance(Config-Router)# Default-Information Originate
VERIFY AND SHOW COMMANDS
Router1#CLEAR IP OSPF PROCESS
Reset ALL OSPF Processes? [No]: Yes
Router2#Clear IP OSPF Process
Reset ALL OSPF Processes? [No]: Yes
TO VERIFY: Which Neighbors Are The OSPD DR/BDR/DROTHER By Using The “Show IP OSPF Neighbor” Command In Privileged Mode.
Router#Show IP OSPF Neighbor
THE “SHOW IP OSPF INTERFACE” Command. This Command Shows Important Information Such As The DR, The BDR, A List Of Neighbors, And The Network Type.
VERIFYING OSPF (THE SHOW COMMAND OPTIONS FOR OSPF): After Two Routers Complete An Initial Exchange Based On Hellos, They Go Through A Process Of Exchanging Information About The Network. After The Routers Have Synchronized Their Information, They Are Adjacent.
◙ - ➤ “SHOW IP OSPF NEIGHBOR” COMMAND: Once You Are Certain The Interfaces Are Properly Assigned And Operational, You Should Check The Status Of The Neighbor’s Adjacency By Using The Show OSPF Neighbor Command, You Can Use “SHOW IP OSPF NEIGHBOR” To Verify And Troubleshoot Neighbor Relationships.
THE FIELDS IN THIS OUTPUT REPRESENT: ADDRESS - > The Physical Interface Ip Address Of The Neighbor Is Displayed In This Column.
INTERFACE - > This Column Shows The Ospf Interface That The Neighbor Is Reachable Across.
STATE - > The Current OSPF Adjacency State Is Displayed Here. The Possible State Values Are Discussed.
ID - > This Field Shows The Router ID Of The Neighbor. This Is Used With The PRI Field To Elect A DR Or BDR On A Broadcast Segment.
PRI - > The Router Priority Is Displayed In This Field. This Value Is Used With The ID Field To Elect A DR Or BDR On A Broadcast Or NBMA Segment.
DEAD - > The Time Remaining Until The Ospf Neighbor Is Declared Unreachable Appears In This Column. Each Received Hello Packet Resets This Timer To The Router Dead Interval Value.
◙ - ➤ “SHOW IP OSPF INTERFACE”COMMAND: This Command Shows Important Information Such As The DR, The BDR, A List Of Neighbors, And The Network Type.
The First Troubleshooting Step Is Often To Determine The State Of The Local Router’s Interfaces. Each Configured OSPF Interface Must Be Operational Before Any Packets Are Sent. A Non-Operational Interface Means That No Neighbors Will Be Located, No Adjacencies Will Form, And The Link-State Database Won’t Be Populated.
The “SHOW IP OSPF INTERFACE” Command Provides Insight Into This Information: THE VARIOUS FIELDS IN THE COMMAND OUTPUT ARE: INTERFACE - > Configured Ospf Interfaces That Are Physically Present In The Router Are Displayed In This Column. Failure To Properly Enter A Logical Unit Value Results In The Interface Not Appearing In This Output.
STATE - > The Current State Of The Interface Is Displayed In This Column. Possible Values Include:
BDR— > The Local Router Is The Backup Designated Router.
DOWN—> The Interface Is Not Currently Operational.
DR— > The Local Router Is The Designated Router.
DROTHER—> The Local Router Is Neither The DR Nor The BDR.
PTTOPT—> This Is A Point-To-Point Interface.
AREA - > This Field Displays The Current Area Id Assigned To The Interface.
DR ID - > The Router ID Of The Current Designated Router Is Displayed In This Column. Point-To Point Interfaces Use A Value Of 0.0.0.0.
BDR ID - > The Router Id Of The Current Backup Designated Router Is Displayed In This Column. Point-To-Point Interfaces Use A Value Of 0.0.0.0.
NBRS - > The Value In This Column Represents The Total Number Of OSPF Neighbors Discovered Across This Interface.
◙ - ➤ “SHOW IP OSPF INTERFACE BRIEF” This “SHOW IP OSPF INTERFACE BRIEF” Command - > (Optional) Displays Brief Overview Information For OSPF Interfaces, States, Addresses And Masks, And Areas On The Router.
This Command Gives A Brief Summary Of What Interface Is Currently Configured With OSPF On The Router, As Well As The IP Address And Subnet Mask Of That Interface.
◙ - ➤ “CLEAR IP OSPF NEIGHBOR” COMMAND: It May Be Necessary To Reset The Peer Session To A Neighbor. This May Occur If The Remote Router Is Malfunctioning Or If You Want To Refresh The Link-State Database With New Information.
This Is Accomplished With The “CLEAR OSPF NEIGHBOR NEIGHBOR-ADDRESS” Command. The Optional Neighbor-Address Switch Clears That Specific Neighbor.
Use The CLEAR IP OSPF NEIGHBOR Command To Clear Neighbor Information From The SHOW IP OSPF NEIGHBOR Command. Use The Instance-Tag Argument To Clear The Neighbor Details From One OSPF Instance. If You Do Not Use The Instance -Tag Argument, Cisco NX-OS Clears The Neighbor Details From All OSPF Instances. Use The Show IP OSPF Neighbor Command To Find The Neighbor ID. This Command Requires The LAN Base Services License.
This Example Shows How To Clear All OSPF Neighbor Details For Neighbor 192.0.2.1 For Instance Tag 201:
Switch# Clear IP OSPF 201 Neighbor 192.0.2.1
This Example Shows How To Clear All OSPF Neighbor Details For All OSPF Instances:
Switch# Clear IP OSPF Neighbor *
This Example Shows How To Clear All OSPF Neighbor Details For All Neighbors On Ethernet Interface 1/2 For OSPF Instance 202:
Switch# Clear IP OSPF 202 Neighbor Ethernet 1/2
TROUBLESHOOTING THE ROUTING PROTOCOL: After The Local Router Has Found Its Neighbors And Formed Its Adjacencies, Flooding Of LSAs Ensues. This Populates The Link-State Database And The Dijkstra Calculation Is Performed. In Addition, The Periodic Transmission Of Hello And Link-State Update Packets Is Performed To Maintain The Adjacencies And The Consistency Of The Database. Various Commands Provide Some Visibility To These Processes.
◙ - ➤ SHOW IP OSPF DATABASE: The Show Ospf Database Command Is An Excellent Tool In Troubleshooting Ospf. If The Information Is Not In The Database, It Will Not Appear In The Routing Table.
The Fields In The Command Output Represent The Following Information: Type The Lsa Type Is Displayed In This Field. The Possible Names Include:
ROUTER—>Type 1 Router Lsa
NETWORK—>Type 2 Network Lsa
SUMMARY—>Type 3 Network Summary Lsa
ASBRSUM—>Type 4 Asbr Summary Lsa
EXTERN—>Type 5 As External Lsa
NSSA—>Type 7 Nssa External Lsa
ID This Field Shows The Link-State Id Field From The Lsa. This Value Is Used To Provide Uniqueness For Each Lsa. Entries Marked With An Asterisk (*) Are LSAS Generated By The Local Router.
ADV RTR The Router Id Of The Originating Router For Each LSA Is Displayed In This Field.
SEQ The Sequence Number Assists The Router To Determine The Most Recent Version Of The LSA.
Age This Field Displays The Current Age Of The Lsa. All Lsas Begin With A Lifetime Of 0 And Increment To A Defined Maxage Of 3600 Seconds. Each LSA Must Be Refreshed Before The Maxage Value Is Reached.
OPT The Options Field From The OSPF Header Is Displayed In This Column. The Possible Bit Values Are Discussed In The “Hello Packet” Section Earlier In This Chapter.
CKSUM The Calculated Checksum Value Of The LSA Is Stored In This Field. Each Router Calculates A New Checksum When The LSA Is Received And Verifies The Value Against The Received Value To Ensure Packet Integrity. Len This Field Displays The Total Length Of The LSA.
◙ - ➤ SHOW IP OSPF LOG: The Show OSPF Log Command Displays How Often The Spf Algorithm Is Being Initiated And How Long Each Operation Takes To Finish.
◙ - ➤ SHOW IP OSPF STATISTICS:
The Show IP OSPF Statistics Command Displays Counters Based On The OSPF Packet Type. Both The Total Number Of Packets And The Number In The Last 5 Seconds Is Shown. Additionally, You Can See The Total Number Of LSA Retransmissions With This Command. If This Value Rapidly Increases, It
Means Your OSPF Neighbor Is Not Acknowledging Its Receipt Of Your LSAs. The Remote Router Is Either Overworked Or Malfunctioning.
◙ - ➤ SHOW IP OSPF ROUTE:
OSPF DESIGN CONSIDERATIONS:
◙ - ➤ By Most Cases, The Optimal Upper Limit For OSPF In The Majority Of Networks Is Area 40 To 50 Routers Per Area, But This Is More Of A Guideline That It Is A Requirement.
◙ - ➤ Your Own Implementations And Use May Vary Depending On What Types Of Routers You're Using.
◙ - ➤ In Most Cases, There Should Not Be Any More Than 100 Routers Per Area, Because The Larger The Area, The Greater The Likelihood For Performance Problems Associated With OSPF Routing Recalculations, And The More Unstable The Area Becomes.
◙ - ➤ But With A More Stable Network Infrastructure In Place, You Can Most Likely Run Many More Routers Per Area.
◙ - ➤ One Important Factor To Consider Before It Becomes A Problem Is Making Sure That The Backbone Area Does Not Grow Too Big.
◙ - ➤ It Is Not A Requirement That Most Routes Should Belong In Area 0.
◙ - ➤ Be Sure To Outline The Logical View Of The Network From The Beginning, And Focus On Which Routes, Routers, And Networks Belong In What Area.
◙ - ➤ Also Be Sure To Start Creating Non-Required Areas Before They Are Needed.
◙ - ➤ It Is Always A Good Idea To Plan For Maximum Growth Coupled With Long-Term Planning At The Beginning Of The Network Design Process.
◙ - ➤ Remember That Planning For Too Much Is Not A Bad Thing To Do.
◙ - ➤ Below Are Cisco's Own Recommendations In Regards To OSPF Network Size Parameters.
SIZE OF OSPF ROUTERS FOR AN AREA’S: ◙ No Morethen 3 Area’s Per Router.
◙ No More Then 50 Router Per Area.
◙ No More Then 60 Neighbours Per Router.
◙ A Router Should Only Be A DR Or BDR For 1 (One LAN) LAN.
◙ Virtual Link Allows For An Area Not To Be Physically Connected To The Backbone ( Area 0)
BELOW TABLE ARE CISCO'S OWN RECOMMENDATIONS IN REGARDS TO OSPF NETWORK SIZE PARAMETERS:
| NETWORK PARAMETER | MINIMUM | AVERAGE | MAXIMUM |
|---|---|---|---|
| ROUTERS PER DOMAIN | 1 | 500 | 1000 |
| ROUTERS PER AREA | 1 | 100 | 350 |
| AREAS PER DOMAIN | 1 | 25 | 75 |
| NEIGHBORS PER ROUTER | 1 | 50 | 100 |
| AREAS PER ROUTER | 1 | 3 | 5 |
◙ - ► For More About - > OSPF STANDARDIZATION REPORT:
MULTIPLE AREA OSPF OVER AN NBMA NETWORK: Another Design Consideration Is The Design Of The NBMA Network As Part Of The OSPF Domain. There Are Two Main Ways To Approach The Inclusion Of An NBMA Network:◙ The NBMA Network Can Be Defined As Area 0. The Reasoning Is That If The NBMA Is Used To Connect All Remote Sites, All Traffic Will Have To Traverse This Network. If The Remote Sites Are Made Satellite Areas, All Traffic Will Have To Traverse The NBMA, So It Makes Sense To Make It The Backbone Area. This Works Well In A Full-Mesh Environment, Although It Results In A Large Number Of LSAs Being Flooded Into The Wan And Puts Extra Demands On The Routers Connecting To The NBMA Network.
◙ In A Hub-And-Spoke NBMA Network, It Makes Sense To Assign The Hub Network As Area 0 With The Other Remote Sites And The NBMA Network As Other Areas. This Is A Good Design If The Satellite Areas Are Stub Areas Because It Means That The Routing Information—And, Thus, Network Overhead—Is Kept To A Minimum Over The NBMA Cloud. Depending On The Design, The Rest Of The Network Might Constitute One Other Area Or Multiple Areas. This Will Depend On The Size And Growth Expectations Of The OSPF Domain.
CONCLUSION:
The Goal Of This Article Is To Give An Easy Way To Understand The “OSPF Configuration Troubleshooting Command References" And Also We Hope This Guide Will Help Every Beginner Who Are Going To Start Cisco Lab Practice Without Any Doubts. Some Topics That You Might Want To Pursue On Your Own That We Did Not Cover In This Article Are Listed Here!Hands - On Experience Is An Invaluable Part Of Preparing For The Lab Exam And Never Pass Up An Opportunity To Configure Or Troubleshoot A Router ( If You Have Access To Lab Facilities, Take Full Advantage Of Them) There Is No Replacement For The Experience You Can Gain From Working In A Lab, Where You Can Configure Whatever You Want To Configure And Introduce Whatever Problems You Want To Introduce, Without Risk Of Disrupting A Production Network. Thank You And Best Of Luck
This Article Written Author By: Mr. Premakumar Thevathasan - CCNA And CCNP (Routing & Switching), MCSE, MCSA, MCSA - MSG, CIW Security Analyst, CompTIA Certified A+ And Etc.
WARNING AND DISCLAIMER:
Routers Direct And Control Much Of The Data Flowing Across Computer Networks. This Guide Provides Technical Guidance Intended To Help All Network Students, Network Administrators And Security Officers Improve Of Their Demonstrated Ability To Achieve Specific objectives Within Set Timeframes.This Document Carries No Explicit Or Implied Warranty. Nor Is There Any Guarantee That The Information Contained In This Document Is Accurate. Every Effort Has Been Made To Make All Articles As Complete And As Accurate As Possible, But No Warranty Or Fitness Is Implied.
It Is Offered In The Hopes Of Helping Others, But You Use It At Your Own Risk. The Author Will Not Be Liable For Any Special, Incidental, Consequential Or Indirect Any Damages Due To Loss Of Data Or Any Other Reason That Occur As A Result Of Using This Document. But No Warranty Or Fitness Is Implied. The Information Provided Is On An "As Is" Basic. All Use Is Completely At Your Own Risk.
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