Some Topics That You Might Want To Pursue On Your Own That We Did Not Cover In This Article Are Listed Here. The Work Described In This Article Is Mainly Focused On The Field Of “SHORT RECAP ABOUT RIP PROBLEM WITH DISTANCE VECTOR ROUTING LOOP”. FOR MORE REFERENCES:
◙ - ➤ Basic Collection Of Networking Concepts:
◙ - ➤ RIPv1 Vs RIPv2 And Vs RIPng:
◙ - ➤ Routing And Switching Command Reference:
◙ - ➤ Basic Router Configuration:◙ - ➤ RIP Configuration:
◙ - ➤ RIP Timer Configuration:
◙ - ➤ RIP MD5:
◙ - ➤ Default-Information-Originate-Command:
SHORT RECAP
◙ ROUTED PROTOCOL: IP/IPX
◙ ROUTING PROTOCOL: RIP, IGRP, EIGRP, OSPF, IS-IS.
TWO CATEGORIES OF ROUTING PROTOCOLS: ◙ EXTERIOR ROUTING PROTOCOLS: Used For Use Between Different Organizations Such As ISPs Or ISPs And Their Customers.
– Ex: BORDER GATEWAY PROTOCOL (BGP)
◙ INTERIOR ROUTING PROTOCOLS: Used To Distribute Routing Information Inside A Single Organization.
– Ex: RIP, IGRP, EIGRP, OSPF, IS-IS
THE INTERIOR ROUTING PROTOCOLS THREE TYPES ARE: – DISTANCE VECTOR
– LINK-STATE
– HYBRID
ROUTING PROTOCOLS CAN BE CLASSIFIED IN TO Distance Vector And Link-State Protocols. This Routing Protocol Selects The Best Routing Path Based On A Distance Metric And An Interface (The Vector) Or Selects The Best Routing Path By Calculating The State Of Each Link In A Path.
Routing Algorithm Can Be Classified As Distance Vector And Link State. Among Distance Vector And Link State Routing, Distance Vector Routing Algorithm Forwards The Information To Each And Every Node From And To Its Neighbors. The Distributed Bellman-Ford Algorithm Is A Well Known Example Of Distance-Vector Algorithm (RIP) Which Calculates The Shortest Path. RIP (Routing Information Protocol) Is A Widely-Used Protocol For Managing Router Information Within A Local Area Network (LAN) Or An Interconnected Group Of LANs. RIP Is An Interior Gateway Protocol. Collecting And Broadcasting The Routing Information May Initiates Count-To-Infinity Problem And Routing Loops. Distance Vector Routing Algorithm Has Very Much Impact On MANET.
In LINK-STATE ROUTING, Each Node Floods The Information To Entire Network. Once Received The Link-State Updates From Other Nodes, Each Node Independently Computes Paths To Destination. The Primary Difference Between Link-State And Distance Vector Routing Is That Link-State Uses Algorithms Derived From The Dijkstra’s Shortest Path Algorithm, Where Distance Vector Uses Distributed Bellman-Ford. The Distance Vector Protocols Start Counting From The Updates Even If The Entire Topology Is Not Known, While Link-State Protocols Find Out The Entire Topology And Then Start Counting, So It Uses More Memory To Keep The Whole Topology Information. Link-State Routing Protocols Don’t Suffer From The Count-To-Infinity Problem.
The DISTANCE VECTOR Uses The Bellman Ford Algorithm For Finding The Shortest Paths. Every Node Counts All Paths To Every Other Router. The Shortest Path Is Based On A Metric. Sometimes The Metric Is Referred In The Routing Literature As A Count Or A Distance. The Main Features Of Distance-Vector Are Iterative, Distributed, And Asynchronous. In Distance Vector The Process Of Exchanging Information Is Done Iteratively That Is Until No More Information Is Exchanged Between The Neighborhoods, The Information Is Distributed Or Received Form One Or More Of Its Node Directly From Its Neighbors And The Algorithm Does Not Require All Of The Nodes To Operate In Lock Step (Asynchronous) With Each Other.
BELLMAN-FORD ALGORITHM The Bellman-Ford Algorithm Solves The Single Source Shortest Path Problems Even In The Cases In Which Edge Weights Are Negative. This Algorithm Returns A Boolean Value Indicating Whether Or Not There Is A Negative Weight Cycle That Is Reachable From The Source. If There Is Such A Cycle, The Algorithm Indicates That No Solution Exists And It There Is No Such Cycle, It Produces The Shortest Path And Their Weights.
The Bellman-Ford algorithm runs in time O(VE), since the initialization takes Θ(V) time, each of the |V| - 1 passes over the edges takes O(E) time and calculating the distance takes O(E) times.
Distance Vector Protocols Advertise Routing Information By Sending Messages, Called Routing Updates, Out The Interfaces On A Router. In A Distance Vector Environment, Routing Updates Are Propagated Only To Directly Connected Neighbors. Pass Periodic Copies Of Full Routing Table To Neighbor Routers And Accumulate Distance Vectors.
◙ - ➤ For More Reference About Protocol Comparison: CLASSLESS ROUTING PROTOCOLS Vs CLASSFUL ROUTING PROTOCOLS: ◙ CLASSFUL ROUTING PROTOCOLS Do Not Carry Subnet Masks Along With Their Updates. Older Routing Protocols, Including RIPv1 And IGRP, Are Classful.
Examples Of Classful Routing Protocols Include RIPv1 And IGRP.
With Classful Routing, Each IP Address Requires Its Own Entry In The Routing Table. With Classless Routing, A Series Of Addresses Can Be Combined Into One Entry Potentially Saving Vast Amounts Of Space In Routing Tables.
◙ CLASSLESS ROUTING PROTOCOLS DO Send The Subnet Mask Along With Their Updates. Newer Protocols, Including RIP-2, EIGRP, And OSPF, Are Classless. Variable Length Subnet Masks (VLSMs) Are Allowed When Using Classless Routing Protocols.
Examples Of Classless Routing Protocols Include RIPv2, EIGRP, OSPF, BGPAnd IS-IS.
Classless Addresses Use A Combination Of IP Address And Netmask. Classless Inter-Domain Routing (CIDR) Was Introduced In 1993 (Originally With RFC 1519 And Most Recently With RFC 4632) To Keep Routing Tables From Getting Too Large.
Current Routing Protocols That Support Classless Routing Out Of Necessity Include Ripv2, BGP, IS-IS, And OSPF.
VARIABLE-LENGTH SUBNET MASKING (VLSM): Means That, In A Single Class A, B, Or C Network, Multiple Subnet Masks Can Be Used.
◙ The Advantage Of VLSM Is That It Enables You To Vary The Size Of Each Subnet, Based On The Needs Of That Subnet.
◙ Some Routing Protocols Support VLSM, And Some Do Not
ADMINISTRATIVE DISTANCE: Is A Selection Method For IP Routing Protocols. The Lower The Administrative Distance, The More Trusted The Learning Mechanism.
–Manually Entered Routes Are Preferred To Dynamically Learned Routes.
–Routing Protocols With Sophisticated Metrics Are Preferred Over Protocols With Simple Metric Structures.
ROUTING INFORMATION PROTOCOL (RIP)
RIP Implements The Split Horizon, Route Poisoning And Hold down Mechanisms To Prevent Incorrect Routing Information From Being Propagated. These Are Some Of The Stability Features Of RIP.
RIP Sends The Complete Routing Table Out To All Active Interfaces Every 30 Seconds. RIP Only Uses Hop Count (The Number Of Routers) To Determine The Best Way To A Remote Network. When A Router Receives A Neighbor's RIP Table, It Uses The Information Provided To Update Its Own Routing Table And Then Sends The Updated Table To Its Neighbors.
RIPv1 Is A Classful Routing Protocol But RIPv2 Is A Classless Routing Protocol.
Classful Routing Protocols Do Not Include The Subnet Mask With The Network Address In Routing Updates, Which Can Cause Problems With Discontiguous Subnets Or Networks That Use Variable-Length Subnet Masking (VLSM). Fortunately, RIPv2 Is A Classless Routing Protocol So Subnet Masks Are Included In The Routing Updates, Making RIPv2 More Compatible With Modern Routing Environments.
◙ RIP Uses Hop Counts To Calculate Optimal Routes (A Hop Is A Router).
◙ RIP Routing Is Limited To 15 Hops To Any Location (16 Hops Indicates The Network Is Unreachable).
◙ RIP Uses The Split Horizon With Poison Reverse Method To Prevent The Count-To-Infinity Problem.
◙ RIP Uses Only Classful Routing, So It Uses Full Address Classes, Not Subnets.
◙ RIP Broadcasts Updates To The Entire Network.
◙ RIP Can Maintain Up To Six Multiple Paths To Each Network, But Only If The Cost Is The Same.
◙ RIP Supports Load Balancing Over Same-Cost Paths.
◙ The Update Interval Default Is 30, The Invalid Timer Default Is 180, The Holddown Timer Default Is 180, And The Flush Timer Default Is 240.
RIPv1 Vs RIPv2
◙ RIP Supports Up To Six Equal-Cost Paths To A Single Destination, Where All Six Paths Can Be Placed In The Routing Table And The Router Can Load-Balance Across Them. The Default Is Actually Four Paths, But This Can Be Increased Up To A Maximum Of Six. Remember That An Equal-Cost Path Is Where The Hop Count Value Is The Same. RIP Will Not Load-Balance Across Unequal-Cost Paths
RIPv2: ◙ RIPv2 Uses Multicasts, Version 1 Use Broadcasts,
◙ RIPv2 Supports Triggered Updates—When A Change Occurs, A Ripv2 Router Will Immediately Propagate Its Routing Information To Its Connected Neighbors.
◙ RIPv2 Is A Classless Protocol. RIPv2 Supports Variable-Length Subnet Masking (VLSM).
◙ RIPv2 Supports Authentication. You Can Restrict What Routers You Want To Participate In RIPv2. This Is Accomplished Using A Hashed Password Value.
RIPng: The Routing Information Protocol Next Generation (RIPng) Is An Interior Gateway Protocol (IGP) That Uses A Distance-Vector Algorithm To Determine The Best Route To A Destination, Using The Hop Count As The Metric. RIPng Is A Routing Protocol That Exchanges Routing Information Used To Compute Routes And Is Intended For Internet Protocol Version 6 (IPv6)-Based Networks.
RIPng IS ENABLED ON EACH INTERFACE: Router1(Config)#IPv6 Router Rip Prem//Name The Process RIPng Prem
Router1(Config-Rtr)#Exit
Router1(Config)#Interface E0/0
Router1(Config-If)#IPv6 Rip Prem Enable //Run RIPng Prem Process On E0/0
PROBLEM WITH DISTANCE VECTOR ROUTING LOOP
SPLIT HORIZON: Split Horizon Is A Method Of Preventing A Routing Loop In A Network. The Basic Principle Is Simple: Information About The Routing For A Particular Packet Is Never Sent Back In The Direction From Which It Was Received.
Routing Information Protocol Uses Split Horizon. In Split Horizon Actual Distance To A Destination Is Not Reported To The Node Through Which It Reaches The Destination. For Example If Node A Has Learned A Route To Node C Through B, Then A Does Not Send The Distance Vector Of C To Node B During A Routing Update.
RIP Functions By Periodically Flooding The Entire Routing Table Out To The Network, It Generates A Lot Of Traffic. The Split Horizon And Poison Reverse Techniques Can Help Reduce The Amount Of Network Traffic Originated By RIP Hosts And Make The Transmission Of Routing Information More Efficient.
If A Router Receives A Set Of Route Advertisements On A Particular Interface, RIP Determines That Those Advertisements Do Not Need To Be Retransmitted Out The Same Interface. This Technique, Known As Split Horizon, Helps Limit The Amount Of RIP Routing Traffic By Eliminating Information That Other Neighbors On That Interface Have Already Learned.
POISON REVERSE: Poisoned Reverse Is An Additional Technique Which Is Used With Split Horizon. With Route Poisoning When A Node Detects That One Of Its Routes Has Failed, The Node Will Poison The Route By Putting The Cost Of The Link To Infinity To It And Advertising It To Neighbors.
When A Node Advertises A Poisoned Route To Its Neighbor’s Nodes, The Neighbor’s Nodes Break The Rule Of Split Horizon And Send Back To The Originator The Same Poisoned Route, Called A Poison Reverse. Split Horizon With Poisoned Reserve Prevents Routing Loops Involving Only Two Nodes, For Loops Involving More Nodes On The Same Link Split Horizon With Poisoned Reverse Will Not Be Sufficient.
Split Horizon With Poison Reverse Is More Effective Than Simple Split Horizon In Networks With Multiple Routing Paths, Although It Affords No Improvement Over Simple Split Horizon In Networks With Only One Routing Path.
The Poison Reverse Technique Helps To Optimize The Transmission Of Routing Information And Improve The Time To Reach Network Convergence. If Router A Learns About Unreachable Routes Through One Of Its Interfaces, It Advertises Those Routes As Unreachable (Hop Count Of 16) Out The Same Interface.
ROUTE POISONING: Route Poisoning Is A Method Of Preventing A Network From Sending Packets Through A Route That Has Become Invalid. When The Routing Protocol Detects An Invalid Route (Such As Can Be Caused By A Severed Cable Or The Failure Of A Network Node), All Of The Routers In The Network Are Informed That The Bad Route Has A Hop Count Of 16, Which Stands For Infinity. This Makes All Nodes On The Invalid Route Appear Infinitely Distant, Thereby Preventing Any Of The Routers From Sending Packets Over The Invalid Route.
Route Poisoning Is Used To Mark The Route As Unreachable In A Routing Update That Is Sent To Other Routers. Unreachable Is Interpreted As A Metric That Is Set To The Maximum. For RIP, A Poisoned Route Has A Metric Of 16.
When The Path Between Two Routers In A Network Goes Bad, All The Routers In The Network Are Informed Immediately. However, It Is Possible For This Information To Be Lost, Causing Some Routers To Once Again Attempt To Send Packets Over The Bad Route. This Requires That They Be Informed Again That The Route Is Invalid, And Again, This Information Can Be Lost. The Resulting Problem Is Known As A Routing Loop. Route Poisoning Is Used In Conjunction With Holddowns. A Holddown Keeps Update Messages From Falsely Reinstating The Validity Of A Bad Route. This Prevents Routing Loops, Improving The Overall Efficiency Of The Network.
Router Consider Route Advertised With An Infinitive Metric To Have Failed ( Metric=16) Instead Of Marking It Down.
Note: ◙ 1. The Split Horizon Rule Says That A Router Should Not Advertise A Network Through The Interface From Which The Update Came.
◙ 2. The Rule For Split Horizon With Poison Reverse States When Sending Updates Out A Specific Interface, Designate Any Networks That Were Learned On That Interface As Unreachable.
◙ 3. Split Horizon With Poison Reverse Is A Combination Of Split Horizon And Route Poisoning. Although The Split Horizon Part Of It Works Differently Then Split Horizon Itself.
COUNTING TO INFINITY/COUNT-TO-INFINITY PROBLEM: Maximum Count 15 Hops After It Will Not Be Reachable.
RIP For IP, Like Most Distance Vector Routing Protocols, Announces Its Routes In An Unsynchronized And Unacknowledged Manner. This Can Lead To Convergence Problems. However, You Can Enable Modifications To The Announcement Algorithms To Reduce Convergence Time In Most Situations.
COUNT-TO-INFINITY PROBLEM: The Classic Distance Vector Convergence Problem Is Known As The Count-To-Infinity Problem And Is A Direct Result Of The Asynchronous Announcement Scheme. When RIP For IP Routers Add Routes To Their Routing Table, Based On Routes Advertised By Other Routers, They Keep Only The Best Route In The Routing Table And They Update A Lower Cost Route With A Higher Cost Route Only If Is Being Announced By The Same Source As The Current Lower Cost Route.
FOR EXAMPLE: Just Imagine A Subnet Connected Like Router A<– /Down ---> Router B <--–-> Router C, And Let The Metric Between The Routers Be "Number Of Jumps".
Now Suppose That Router A Is Taken Offline. In The Vector-Update-Process Router B Notices That The Route To The Router A, Which Was Distance 1, And It Is Down Router B Does Not Receive The Vector Update From Router A.
The Problem Is, Router B Also Gets An Update From Router C, And Router C Is Still Not Aware Of The Fact That Router A Is Down So It Tells Router B That Router A Is Only Two Jumps From Router C (C To B To A), Which Is False.
This Slowly Propagates Through The Network Until It Reaches Infinity (In Which Case The Algorithm Corrects Itself, Due To The Relaxation Property Of Bellman–Ford).
When Routers Count To Infinity, They Collectively Keep Changing Their Minds About The Metric Of A Failed Route. The Metric Grows Until It Reaches Infinity, At Which Point The Routers Finally Believe That The Route Has Failed.
Note: Split Horizon With Poison Reverse Differs From Simple Split Horizon Because It Announces All Networks. However, Those Networks Learned In A Given Direction Are Announced With A Hop Count Of 16, Indicating That The Network Is Unreachable. In A Single-Path Internetwork, Split Horizon With Poison Reverse Has No Benefit Beyond Split Horizon. However, In A Multipath Network, Split Horizon With Poison Reverse Greatly Reduces Count-To-Infinity And Routing Loops. Count-To-Infinity Can Still Occur In A Multipath Internetwork Because Routes To Networks Can Be Learned From Multiple Sources.
HOLD DOWN TIMERS: The Count To Infinity Problem Can Be Avoided By Using Hold Down Timers. This Is A Clock That Is Set Within The Node To Help Ensure Network Stability. When A Node Receives An Update From A Neighbor Indicating That A Previously Accessible Network Is Not Working And Is Inaccessible, The Hold-Down Timer Will Start. If A New Update Arrives From A Neighbor With A Better Metric Than The Original Network Entry, The Hold-Down Is Removed And Data Is Passed. But An Update Is Received From A Neighbor Node Before The Hold-Down Timer Expires And It Has A Lower Metric Than The Previous Route, Therefore The Update Is Ignored And The Hold-Down Timer Keeps Ticking. This Allows More Time For The Network To Converge.
The Default Hold-Down Timer Value = 180 Second.
TRIGGERED UPDATE: Triggered Updates Allow A RIP Router To Announce Changes In Metric Values Almost Immediately Rather Than Waiting For The Next Periodic Announcement. The Trigger Is A Change To A Metric In An Entry In The Routing Table. When Any Route Failed In Network, Do Not Wait For The Next Periodic Update Instead Send An Immediate Update Listing The Poison Route.
Triggered Updates States That "Counting To Infinity Is Still Possible", Even With These Mechanisms. When A Node Receives A Update, It Counts The Shortest Path Again. If The Counting Results In As A Change Of The Metric, That Is, A New Shortest Path Is Found, The Node Sends Updates To The Network. The Problem With This Approach Is That Routes Can Change Also While The Triggered Updates Are Being Sent.
RIP CONFIGURATION:
| Router(Config)#Router RIP | Enter router RIP configuration mode |
| Router(Config-Router)#Network <address> | Identify Networks That Will Participate In The Router Protocol. Notice That You Identify Networks, And Not Interfaces. |
◙ - ► For More About - > RIP Notes And RIP Configuration:
RIP - SUMMARY AND REVIEW QUESTIONS
• Request For Comments (RFC) 1058
• Internet Standard (STD)
✓ It Uses Distance Vectors To Mathematically Compare Routes To Identify The Best Path To Any Given Destination Address
✓ With The Expansion Of IP Based Networks (More Numerous And Greater In Size)
✓ Update In 1994
✓ RIP2 Defined In 1994 In RFC 1723
✓ The Routing Information Protocol (RIP) Is A Distance-Vector, Interior Gateway (IGP) Routing Protocol Used By Routers To Exchange Routing Information.
✓ RIP Uses The Hop Count As A Routing Metric.
✓ RIP Prevents Routing Loops By Implementing A Limit On The Number Of Hops Allowed In A Path From The Source To A Destination. The Maximum Number Of Hops Allowed For RIP Is 15.
This Hop Limit, However, Also Limits The Size Of Networks That RIP Can Support.RIP Version 2 (RIPv2) Was Developed Due To The Deficiencies Of The Original RIP.
DIFFERENCE BETWEEN RIPv1 Vs RIPv2: ✓ RIPv1 Is Classful Routing Protocol And RIPv2 Classless Routing Protocol.
✓ In RIPv1, Subnet Masks Are NOT Included In The Routing Update And In RIPv2 Subnet Masks Are Included In The Routing Update.
✓ RIPv2 Multicasts The Entire Routing Table To All Adjacent Routers At The Address 224.0.0.9, As Opposed To RIPv1 Which Uses Broadcast (255.255.255.255). Unicast Addressing Is Still Allowed For Special Applications.
◙ - ► For More About - > DEFERENCE BETWEEN RIPv1 vs RIPv2 And vs RIPng:
◙ - ► For More About - > RIP (IPv4) Vs RIPv3 (IPv6):
◙ - ► For More About - > RIP TIMERS:
BASIC CONFIGURATION: ✓ Cisco IOS, Uses "Router RIP" Command To Enable Rip Routing Protocol. The Version Command Is Used To Specify Which RIP Version To Use (Either 1 Or 2). If The Version Command Is Omitted Then The Router Defaults To Sending RIPv1 But Can Receive Both RIPv1 And RIPv2.✓ The "Network" Command Is Used To Specify The Directly Connected Subnets On The Router To Be Configured And That Are Intended To Be Included In The Routing Updates.
✓ According To The Classful, Network Specified, The Subnets Of That Network Are Automatically Identified And Participate In The Routing Update. By Default Routing Updates Are Summarized At Network Boundaries.
✓ In RIPv2 This Auto Summarization Behavior Can Be Turned Off Using The "No Auto-Summary" Command. Moreover, Manual Summarization Can Be Configured On A Per Interface Level.
CONFIGURATION EXAMPLE: R1#Conf T
R1(Config)#Router Rip
R1(Config-Router)#Version 2
R1(Config-Router)#Network 192.168.12.0
R1(Config-Router)#Exit
RIP VERIFICATION: R1#Show IP Protocol
◙ - ► For More About - > RIP IP Split Horizon Notes:
◙ - ► RIP Configuration Example:
◙ - ► RIP Message Digest 5 (MD5) Authentication:
1. WHAT PORT DOES RIP USE? Answer: RIP Uses UDP Port 520.
2. WHAT METRIC DOES RIP USE? HOW IS THE METRIC USED TO INDICATE AN UNREACHABLE NETWORK? Answer: RIP Uses A Hop Count Metric. An Unreachable Network Is Indicated By Setting The Hop Count To 16,Which RIP Interprets As An Infinite Distance.
3. WHAT IS THE UPDATE PERIOD FOR RIP? Answer: RIP Sends Periodic Updates Every 30 Seconds Minus A Small Random Variable To Prevent The Updates Of Neighboring Routers From Becoming Synchronized.
4. HOW MANY UPDATES MUST BE MISSED BEFORE A ROUTE ENTRY WILL BE MARKED AS UNREACHABLE? Answer: A Route Entry Is Marked As Unreachable If Six Updates Are Missed.
5. WHAT IS THE PURPOSE OF THE GARBAGE COLLECTION TIMER? Answer: The Garbage Collection Timer, Or Flush Timer, Is Set When A Route Is Declared Unreachable. When The Timer Expires, The Route Is Flushed From The Route Table. This Process Allows An Unreachable Route To Remain In The Routing Table Long Enough For Neighbors To Be Notified Of Its Status.
6. WHY IS A RANDOM TIMER ASSOCIATED WITH TRIGGERED UPDATES? WHAT IS THE RANGE OF THIS TIMER? Answer: The Random Timer, Whose Range Is 1 To 5 Seconds, Prevents A "Storm" Of Triggered Updates During A Topology Change.
7. WHAT IS THE DIFFERENCE BETWEEN A RIP REQUEST MESSAGE AND A RIP RESPONSE MESSAGE? Answer: A Request Message Asks A Router For An Update. A Response Message Is An Update.
8. WHICH TWO TYPES OF REQUEST MESSAGES DOES RIP USE? Answer: A Request Message May Either Ask For A Full Update Or In Some Special Cases It May Ask For Specific Routes.
9. UNDER WHAT CIRCUMSTANCES WILL A RIP RESPONSE BE SENT? Answer: A Response Is Sent When The Update Timer Expires, Or Upon Reception Of A Request Message.
10. WHY DOES RIP HIDE SUBNETS AT MAJOR NETWORK BOUNDARIES? Answer: ✓ RIP Updates Do Not Include The Subnet Mask Of The Destination Address, So A RIP Router Depends On The Subnet Masks Of Its Own Interfaces To Determine How An Attached Major Network Address Is Subnetted.
✓ If A Router Does Not Have An Attachment To A Particular Major Network Address, It Has No Way To Know How That Major Network Is Subnetted. Therefore, No Subnets Of A Major Network Address Can Be Advertised Into Another Major Network.
11. WHAT ARE TWO CHARACTERISTICS OF RIPV2? (CHOOSE TWO)? A. Classful Routing Protocol
B. Variable-Length Subnet Masks
C. Broadcast Addressing
D. Manual Route Summarization
E. Uses SPF Algorithm To Compute Path
Answer: B D
12. AFTER A RIP ROUTE IS MARKED INVALID ON ROUTER_1, HOW MUCH TIME WILL ELAPSE BEFORE THAT ROUTE IS REMOVED FROM THE ROUTING TABLE? Router_1# Show IP Protocols
Routing Protocol Is “Rip”
Sending Updates Every 30 Seconds, Next Due In 8 Seconds
Invalid After 180 Seconds, Hold Down 180, Flushed After 240
Outgoing Update Filter List For All Interfaces Is Not Set
Incoming Update Filter List For All Interfaces Is Not Set
A. 30 Seconds
B. 60 Seconds
C. 90 Seconds
D. 180 Seconds
E. 240 Seconds
Answer: B
Explanation: The Invalid And Flush Timers Start At The Same Time And Run Concurrently. So After A RIP Route Is Marked Invalid, It Will Take 240 – 180 = 60 Seconds For That Route To Be Removed From The Routing Table.
13. WHAT IS THE DEFAULT ROUTING UPDATE PERIOD FOR RIPV2? A. 15 Seconds
B. 30 Seconds
C. 180 Seconds
D. 240 Seconds
Answer: B
14. WHAT TWO THINGS WILL A ROUTER DO WHEN RUNNING A DISTANCE VECTOR ROUTING PROTOCOL? (CHOOSE TWO)? A. Send Periodic Updates Regardless Of Topology Changes.
B. Send Entire Routing Table To All Routers In The Routing Domain.
C. Use The Shortest-Path Algorithm To The Determine Best Path.
D. Update The Routing Table Based On Updates From Their Neighbors.
E. Maintain The Topology Of The Entire Network In Its Database.
Answer: A D
15. WHICH STATEMENT ABOUT RIPng IS TRUE? A. Ripng Allows For Routes With Up To 30 Hops.
B. RIPng Is Enabled On Each Interface Separately.
C. RIPng Uses Broadcasts To Exchange Routes.
D. There Can Be Only One RIPng Process Per Router.
Answer: B
16. WHICH THREE STATEMENTS ARE CORRECT ABOUT RIP VERSION 2? (CHOOSE THREE) A. It Has The Same Maximum Hop Count As Version 1.
B. It Uses Broadcasts For Its Routing Updates.
C. It Is A Classless Routing Protocol.
D. It Has A Lower Default Administrative Distance Than RIP Version 1.
E. It Supports Authentication.
F. It Does Not Send The Subnet Mask In Updates.
Answer: A C E
17. WHAT IS A ROUTING PROTOCOL? Answer: A Routing Protocol Is A “Language” That Routers Speak To Each Other To Share Information About Network Destinations.
18. WHAT BASIC PROCEDURES SHOULD A ROUTING ALGORITHM PERFORM? Answer: At A Minimum, A Routing Protocol Should Define Procedures For
Passing Reachability Information About Networks To Other Routers.
Receiving Reachability Information From Other Routers.
Determining Optimal Routes Based On The Reachability Information It Has And For Recording This Information In A Route Table.
Reacting To, Compensating For, And Advertising Topology Changes In A Network.
19. WHY DO ROUTING PROTOCOLS USE METRICS? Answer:A Route Metric, Also Called A Route Cost Or A Route Distance, Is Used To Determine The Best Path To A Destination. Best Is Defined By The Type Of Metric Used.
20. WHAT IS CONVERGENCE TIME? Answer: Convergence Time Is The Time A Group Of Routers Takes To Complete The Exchange Of Routing Information.
21. WHAT IS LOAD BALANCING? NAME FOUR DIFFERENT TYPES OF LOAD BALANCING? Answer: Load Balancing Is The Process Of Sending Packets Over Multiple Paths To The Same Destination. Four Types Of Load Balancing Are:
Equal Cost, Per Packet.
Equal Cost, Per Destination.
Unequal Cost, Per Packet.
Unequal Cost, Per Destination.
22. WHAT IS A DISTANCE VECTOR ROUTING PROTOCOL? Answer: A Distance Vector Protocol Is A Routing Protocol In Which Each Router Calculates Routes Based On The Routes Of Its Neighbors And Then Passes Its Routes To Other Neighbors.
23. SEVERAL PROBLEMS ASSOCIATED WITH DISTANCE VECTOR PROTOCOLS? Answer: Several Problems Associated With Distance Vector Protocols Are :
A Susceptibility To Incorrect Routing Information Because Of Its Dependence On Neighbors For Correct Information.
Slow Convergence.
Route Loops.
Counting To Infinity.
24.WHAT ARE NEIGHBORS? Answer: Neighbors Are Routers Connected To The Same Data Link.
25. WHAT IS THE PURPOSE OF ROUTE INVALIDATION TIMERS? Answer: Route Invalidation Timers Delete Routes From A Route Table If They Exceed A Certain Age.
26. EXPLAIN THE DIFFERENCE BETWEEN SIMPLE SPLIT HORIZON AND SPLIT HORIZON WITH POISONED REVERSE? Answer:Simple Split Horizon Does Not Send Route Information Back To The Source Of The Route Information. Split Horizon With Poisoned Reverse Sends The Information Back To The Source But Sets The Metric To Unreachable.
27. WHAT IS THE COUNTING-TO-INFINITY PROBLEM, AND HOW CAN IT BE CONTROLLED? Answer:Counting To Infinity Occurs When Routes Update A Route Over A Loop; Each Router Increases The Metric Of The Route Until The Metric Reaches Infinity. The Effects Of Counting To Infinity Are Controlled By Defining Infinity As A Fairly Low Metric So That Infinity Is Reached Fairly Quickly And The Route Is Declared Unreachable.
28. WHAT ARE HOLDDOWN TIMERS, AND HOW DO THEY WORK? Answer:Holddown Timers Help Prevent Routing Loops. If A Route Is Declared Unreachable Or If The Metric Increases Beyond A Certain Threshold, A Router Will Not Accept Any Other Information About That Route Until The Holddown Timer Expires. This Approach Prevents The Router From Accepting Possibly Bad Routing Information While The Network Is Reconverging.
29. WHAT ARE THE DIFFERENCES BETWEEN DISTANCE VECTOR AND LINK STATE ROUTING PROTOCOLS? Answer:A Distance Vector Router Sends Its Entire Route Table, But It Only Sends The Table To Directly Connected Neighbors. A Link State Router Sends Only Information About Its Directly Connected Links, But It Floods The Information Throughout The Networking Area. Distance Vector Protocols Usually Use A Variant Of The Bellman-Ford Algorithm To Calculate Routes, And Link State Protocols Usually Use A Variant Of The Dijkstra Algorithm To Calculate Routes.
ALSO FOR MORE REFERENCES QUESTIONS AND ANSWERS:
◙ - ➤ IP Routing (BASIC) Questions And Answers With Routing & Switching:
◙ - ➤ Questions And Answers With - (IP ROUTING, IP ADDRESSES, RIP, IGRP, EIGRP, OSPF, BGP, IS-IS):
◙ - ➤ Question And Answers With OSPF:
◙ - ➤ Review Questions And Answers With OSPF:◙ - ➤ Question And Answers With BGP:
◙ - ➤ Question And Answers With VLAN:
◙ - ➤ IPv6 Configuration Commands References:
◙ - ➤ Questions And Answer With IPv6:
CONCLUSION:
The Goal Of This Article Is To Give An Easy Way To Understand The “Short Recap About RIP Problem With Routing Loop” 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: Premakumar Thevathasan - CCNA, CCNP, 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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