CCNP ROUTING INTERVIEW QUESTIONS

Most Important Frequently Asked Ccnp Routing Interview Questions

Interview Quesions on Ccnp Routing

1. Question 1. What Is Routing?

   Answer :

   Routing is the process in which items are forwarded from one location to another. Routing is a hop-by-hop paradigm.

   A Cisco router performs routing and switching functions. Describe what each function does.

   Routing is a way to learn and maintain awareness of the network topology. Each router maintains a routing table in which it looks up the destination Layer 3 address to get the packet one step closer to its destination.

   The switching function is the actual movement of temporary traffic through the router, from an inbound interface to an outbound interface.

2. Question 2. What Are The Three Types Of Routes You Can Use In A Cisco Router?

   Answer :

   The three types of routes are static routes, dynamic routes, and default routes.

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3. Question 3. What Is The Difference Between Static And Dynamic Routes?

   Answer :

   Static routes are routes that an administrator manually enters into a router. Dynamic routes are routes that a router learns automatically through a routing protocol.

4. Question 4. What Is A Default Route?

   Answer :

   Also known as the gateway of last resort, a default route is a special type of static route with an all-zeros network and network mask. The default route is used to route any packets to a network that a router does not directly know about to a next-hop router. By default, if a router receives a packet to a destination network that is not in its routing table, it drops the packet. When a default route is specified, the router does not drop the packet. Instead, it forwards the packet to the IP address specified in the default route.

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5. Question 5. What Is A Routing Protocol?

   Answer :

   A Routing protocol defines the set of rules used by a router when it communicates with neighboring routers. Routing protocols listens for packets from other participants in order to learn and maintain a routing table.

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6. Question 6. What Is Administrative Distance?

   Answer :

   Administrative distance (AD) is an integer from 0 to 255 that rates the trustworthiness of routing information received on a router from a neighboring router. The AD is used as the tiebreaker when a router has multiple paths from different routing protocols to the same destination. The path with the lower AD is the one given priority.

7. Question 7. What Are The Three Classes Of Routing Protocols?

   Answer :

   • Distance vector
   • Link-state
   • Balanced hybrid

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8. Question 8. What Is The Ad For Each Of The Following?

   Answer :

   1. Directly connected interface 0
   2. Static route 1
   3. EIGRP 90
   4. IGRP 100
   5. OSPF 110
   6. RIP 120
   7. External EIGRP 170
   8. Unknown 255

9. Question 9. How Do Distance Vector Routing Protocols Function?

   Answer :

   Also known as Bellman-Ford-Fulkerson algorithms, distance vector routing protocols pass complete routing tables to neighboring routers. Neighboring routers then combine the received routing table with their own routing table. Each router receives a routing table from its directly connected neighbor. Distance vector routing tables include information about the total cost and the logical address of the first router on the path to each network they know about.

CWNA (Certified Wireless Network Administrator) Interview Questions

10. Question 10. How Do Distance Vector Routing Protocols Keep Track Of Any Changes To The Internetwork?

    Answer :

    Distance vector routing protocols keep track of an internetwork by periodically broadcasting updates out all active interfaces. This broadcast contains the entire routing table. This method is often called routing by rumor. Slow convergence of distance vector routing protocols can cause inconsistent routing tables and routing loops.

11. Question 11. What Is Split Horizon?

    Answer :

    The rule of split horizon is that it is never useful to send information about a route back in the direction from which the original update came.

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12. Question 12. What Is Convergence?

    Answer :

    Convergence is when all routers have consistent knowledge and correct routing tables.

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13. Question 13. What Is Route Poisoning?

    Answer :

    With route poisoning, when a distance vector routing protocol notices that a route is no longer valid, the route is advertised with an infinite metric, signifying that the route is bad. In RIP, a metric of 16 is used to signify infinity. Route poisoning is used with holddowns.

14. Question 14. What Are Hold-down Timers?

    Answer :

    Hold-down timers prevent regular update messages from reinstating a route that might have gone bad. Hold-down timers also tell routers to hold for a period of time any changes that might affect routes.

15. Question 15. What Are Triggered Updates?

    Answer :

    When a router notices that a directly connected subnet has changed state, it immediately sends another routing update out its other interfaces rather than waiting for the routing update timer to expire. Triggered updates are also known as Flash updates.

Border Gateway Protocol (BGP) Interview Questions

16. Question 16. What Is Ip Rip?

    Answer :

    IP RIP is a true distance vector routing protocol that sends its complete routing table out all active interfaces every 30 seconds. IP RIP uses a hop count as its metric to determine the best path to a remote network. The maximum allowable hop count is 15, meaning that 16 is unreachable. There are two versions of RIP. Version 1 is classful, and version 2 is classless. IP RIP can load-balance over as many as six equal-cost paths.

17. Question 17. What Four Timers Does Ip Rip Use To Regulate Its Performance?

    Answer :

    Here are the four timers that IP RIP uses to regulate its performance:

    1. Route update timer Time between router updates. The default is 30 seconds.
    2. Route invalid timer Time that must expire before a route becomes invalid. The default is 180 seconds.
    3. Route hold-down timer If IP RIP receives an update with a hop count higher than the metric recorded in the routing table, the router goes into holddown for 180 seconds.
    4. Route flush timer Time from when a route becomes invalid to when it is removed from the routing table. The default is 240 seconds.

Enhanced Interior Gateway Routing Protocol (EIGRP) Interview Questions

18. Question 18. How Do You Stop Rip Updates From Propagating Out An Interface On A Router?

    Answer :

    Sometimes you do not want RIP updates to propagate across the WAN, wasting valuable bandwidth or giving out valuable information about your internetwork. The easiest way to stop RIP updates from propagating out an interface is to use the passive-interface global configuration command.

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19. Question 19. How Do You Display The Contents Of A Cisco Ip Routing Table?

    Answer :

    The show ip route command displays the Cisco routing table’s contents.

20. Question 20. What Is Interior Gateway Routing Protocol (igrp)?

    Answer :

    IGRP is a Cisco proprietary distance vector routing protocol. IGRP has a default hop count of 100 hops, with a maximum hop count of 255. IGRP uses bandwidth and line delay as its default metric, but it can also use reliability, load, and MTU.

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21. Question 21. How Do You Enable Igrp On A Cisco Router?

    Answer :

    The way you enable IGRP on a Cisco router is similar to the way you enable RIP, except you specify IGRP as the protocol and add an autonomous system number.

    For example: RouterA(config)#router igrp 10 (10 is the AS number)

    RouterA(config-router)#network 192.168.0.0

    RouterA(config-router)#network 192.168.1.0

    RouterA(config-router)#network 192.168.2.0

22. Question 22. What Four Timers Does Igrp Use To Regulate Its Performance?

    Answer :

    The four timers IGRP uses to regulate its performance are as follows:

    1. Route update timer Time between router updates The default is 90 seconds.
    2. Route invalid timer Time that must expire before a route becomes invalid . The default is 270 seconds.
    3. Route hold-down timer If a destination becomes unreachable, or if the next-hop router increases the metric recording in the routing table, the router goes into holddown for 280 seconds.
    4. Route flush timer[md]Time from when a route becomes invalid to when it is removed from the routing table. The default is 630 seconds.

23. Question 23. What Are Broadcast Domains?

    Answer :

    A broadcast domain defines a group of devices that receive each others’ broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower your network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.

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24. Question 24. What Devices Are Used To Break Up Collision And Broadcast Domains?

    Answer :

    Switches and bridges are used to break up collision domains. They create more collision domains and fewer collisions. Routers are used to break up broadcast domains. They create more broadcast domains and smaller broadcast areas.

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25. Question 25. How Do The Different Layers Of The Osi Model Communicate With Each Other?

    Answer :

    Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer). For example, the presentation layer can communicate with only the application layer, session layer, and presentation layer on the machine it is communicating with. These layers communicate with each other using protocol data units (PDUs). These PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).

26. Question 26. What Does The Eigrp Stuck In Active Message Mean?

    Answer :

    1. When EIGRP returns a stuck in active (SIA) message, it means that it has not received a reply to a query. An EIGRP neighbour (or neighbours) have not replied to the query for that route.
    2. When the SIA occurs, the router clears the neighbour that did not reply to the query.

27. Question 27. Why Do You Not See Ospf Neighbours As Full/dr Or Full/bdr On Serial Link?

    Answer :

    This is normal. On point-to-point and point-to-multipoint networks, there are no designated routers (DRs) or backup designated routers (BDRs).

CWNA (Certified Wireless Network Administrator) Interview Questions

28. Question 28. What Is Type-1 And Type-2 Lsas In Ospf?

    Answer :

    • Type-1 LSAs are router LSAs and are generated by each router for the area to which the router belongs.
    • Type-2 LSAs are network LSAs and are generated by the DR and BDR.

29. Question 29. What Is Ospf Network Types?

    Answer :

    1. Broadcast, multi-access networks: Ehternet, token ring. Single mode operation.
    2. Point-to-point : T1 CAS, ISDN BRI/PRI, single operation mode, no DR/BDR.
    3. Non-broadcast multi-access(NBMA) networks: Frame realy, ATM, MPLS. Five modes of operation.

30. Question 30. Explain The Function Of A Rendezvous Point ?

    Answer :

    A RP is the focal point for multicast traffic. Traffic is forward to the RP from multicast sources. The RP then forwards traffic to multicast receivers.

31. Question 31. What Is The Purpose Of The Interface Command Ip Multicast Spares-dense-mode ?

    Answer :

    Used with PIMSM Auto-RP and version 2. if the RPs fail, the router reverts to dense mode.

32. Question 32. Describe The Operation Of Anycast Rp?

    Answer :

    Two or more RPs are configured with the same IP address. The IP addresses of the RPs are advertised using a unicast IP routing protocol. Each multicast router chooses the closet RP. If an RP fails, the routers switch to the next nearest RP after the unicast ip routing protocol converges. The MSDP is used between RPs to exchange active multicast source information.

33. Question 33. What Protocols Do Switches Use To Prevent The Broadcasting Of Multicast Traffic ?

    Answer :

    CGMP and IGMP Snooping.

Network Administrator Interview Questions

34. Question 34. Why Are The Cisco Multicast Routing Protocols Referred To As Protocol Independent ?

    Answer :

    Multicast forwarding decisions are based on the entries in the unicast IP routing table. Multicast is not dependent on how the unicast IP routing table was built; you cans use any dynamic interior routing protocol, static routes, or a combination of the two.

35. Question 35. Why Is Bgp A Better Choice For Internet Routing Than The Igps?

    Answer :

    RIP version 1 and IGRP are classful protocols and do not advertise subnet mask information.

    RIP version 2 has a limited network diameter of 15 hops. EIGRP, OSPF, and IS-IS use computational intensive algorithms for determining a shortest path. BGP relies on simple techniques for best path selection and loop detection, and can handle the number of network prefixes required for Internet routing.

36. Question 36. What Is The Major Difference Between Bgp And Igp Route Summarization?

    Answer :

    When a summary address is created with an IGP (EIGRP, OSPF, and IS-IS), the specific routes of the summary are not advertised. BGP advertises the summary, and all the specific routes of the summary unless they are specifically suppressed.

Border Gateway Protocol (BGP) Interview Questions

37. Question 37. Why Does Ibgp Require A Full Mesh?

    Answer :

    BGP uses the AS _PATH attribute for loop detection. If a router sees its own AS number in a BGP advertisement, the advertisement is dropped. IBGP routers have the same AS number so the AS number cannot be used for loop detection. IBGP neighbors will not advertise prefixes learned from one IBGP neighbor to another IBGP neighbor; therefore, a full mesh is required.

38. Question 38. Name Two Methods For Reducing The Number Of Ibgp Connections?

    Answer :

    Route reflector and confederation.

39. Question 39. What Is Synchronization?

    Answer :

    Synchronization is a property of IBGP. An IBGP router will not accept a prefix received from an IBGP neighbor if the prefix is not already in the IP routing table.

40. Question 40. What Is The First Thing That Bgp Checks To Determine If A Prefix Is Accessible?

    Answer :

    BGP checks the NEXT HOP attribute to determine if the NEXT HOP is accessible or in the IP routing table.

Enhanced Interior Gateway Routing Protocol (EIGRP) Interview Questions

41. Question 41. Name All The Ways For Installing A Prefix In The Bgp Routing Table?

    Answer :

    1. Using the network command to transfer a router from the IP routing table to the BGP routing table.
    2. Redistributing routes from the IP routing table to the BGP routing table .
    3. Learned from a BGP neighbor.

42. Question 42. What Is The Order Of Preference For The Bgp Attributes As_path, Local_pref, Med, And Weight?

    Answer :

    WEIGHT, LOACL_PREF, AS_PATH, MED

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43. Question 43. What Is The Purpose Of The Metric Or Multi_exit_disc Attribute?

    Answer :

    MED is used to prefer a path into an autonomous system. A lower MED value is preferred.

44. Question 44. What Is The Scope Of The Local_pref Attribute?

    Answer :

    The LOCAL _PREF attribute is advertised throughout the autonomous system.

45. Question 45. What Is The Purpose Of The Local_pref Attribute?

    Answer :

    If a router has more than one route to the same IP prefix, the best path is the one with the highest LOCAL_PREF (assuming the WEIGHT attribute for the routes is equal).

46. Question 46. What Is The Scope Of The Weight Attribute?

    Answer :

    WEIGHT has only local significance and is not advertised to BGP peers.

47. Question 47. What Is The Purpose Of The Weight Attribute?

    Answer :

    If a router has more than one route to the same IP prefix, the best path is the one with the highest WEIGHT value.

48. Question 48. What Is The Purpose Of The As_path Attribute?

    Answer :

    If a router has more than one route to the same IP prefix, the best path is the one with the shortest AS _PATH (assuming other BGP attributes are equal).

49. Question 49. Describe Four Differences Between The Operation Of Ibgp And Ebgp?

    Answer :

    1. IBGP is the protocol used between routers in the same autonomous system. EBGP is the protocol used between routers in different autonomous systems.
    2. IBGP routes must be synchronized before they can be transferred to the IP routing table (unless synchronization is disabled).
    3. EBGP sets the next hop attribute to the IP address of the interface used to communicate with the EBGP peer. The next hop attribute is not modified when an IBGProuter advertises a prefix to an IBGP peer if the prefix was learned from an EBGP neighbor.
    4. EBGP advertises all prefixes learned from an EBGP neighbor to all other EBGP neighbors. IBGP routers do not advertise prefixes learned from one IBGP neighbor to another IBGP neighbor

50. Question 50. How Many Ospf Databases Are On An Ospf Router?

    Answer :

    The number of OSPF databases on a router is equal to the number of OSPF areas configured on the router.

51. Question 51. What Is The Administrative Distance Of Ospf Routes?

    Answer :

    110

52. Question 52. If A Router Learns About The Same Network Prefix Through Rip, Igrp, Eigrp, And Ospf, Which Route Will Be Preferred?

    Answer :

    • EIGRP has an administrative distance of 90
    • IGRP has an administrative distance of 100.
    • OSPF has an administrative distance of 110.
    • RIP has an administrative distance of 120.
    • Therefore, the EIGRP route is preferred.

53. Question 53. Describe The Structure And Format Of An Nsap Address?

    Answer :

    An NSAP address has a length of8 to 20 bytes and consists of three components:

    One to 13 byte area id

    Six byte system id

    One byte NSAP selector that is always equal to zero for a router

54. Question 54. Describe The Difference Between An Ospf And Is-is Backbone?

    Answer :

    OSPF has a backbone area or area O. All nonzero areas must be connected to the backbone through a router or a virtual link. IS-IS has a backbone area made up ofa contiguous chain of Level 2 capable routers.

55. Question 55. In Is-is, What Does Level 1 Routing Mean?

    Answer :

    Level 1 routing is routing between destinations in the same IS-IS area.

56. Question 56. What Is The Ospf Counterpart To Level L Routing?

    Answer :

    Intra-area routing.

57. Question 57. In Is-is, What Is The Function Of A Level 1-2 Router?

    Answer :

    A Level 1-2 router has two IS-IS databases. The Level l database is used for routing to destinations within the router's configured area. The Level 2 database is used to route between destinations in different areas.

58. Question 58. What Is The Ospf Counterpart To A Level 1-2 Is-is Router?

    Answer :

    An Area Border Router (ABR).

59. Question 59. What Is The Difference Between The Types Of Routes Allowed By Default Into Is-is And Ospf Areas?

    Answer :

    By default, all routes are advertised into all OSPF areas. This includes inter area OSPF routes and external routes that have been injected into OSPF. By default, IS-IS does not advertise inter area or external routes into an area, but injects a default route.

60. Question 60. What Is Route Leaking?

    Answer :

    Redistribution of Level 2 routes into an area as Level l routes.

61. Question 61. Compare Is-is Metrics With Ospf Metrics?

    Answer :

    An OSPF interface metric is determined from the interface bandwidth. By default, all IS¬-IS interface metrics are equal to 10. Therefore, the EIGRP route is preferred.

62. Question 62. What Is The Difference Between An Is-is Narrow And Wide Metric?

    Answer :

    A narrow metric uses 6 bits for the interface metric and 10 bits for the path metric. A wide metric uses 24 bits for the interface metric and 32 bits for the path metric.

63. Question 63. What Types Of Routes Are Allowed Into A Stub Area?

    Answer :

    OSPF intra-area and inter area routes, and a default route. External routes are not advertised into a stub area.

64. Question 64. What Types Of Routes Are Allowed Into A Totally Stubby Area?

    Answer :

    OSPF intra-area routes and a default route. OSPF inter area and external routes are not advertised into a totally stubby area.

65. Question 65. What Types Of Routes Are Allowed Into A Nssa?

    Answer :

    OSPF intra-area and inter area routes, and possibly a default route. External routes from ABRs are blocked, and external routes from ASBRs are converted to Nl or N2 routes.

66. Question 66. What Types Of Routes Are Allowed Into A Totally Nssa?

    Answer :

    OSPF intra-area routes and a default route. External routes from ABRs are blocked, and external routes from ASBRs are converted to Nl or N2 routes.

67. Question 67. What Is The Difference Between An El And E2 Ospf Route?

    Answer :

    An El route contains the OSPF cost to reach the ASBR plus the cost from the ASBR to the external route. An E2 route contains only the cost from the ASBR to the external route.

68. Question 68. What Are The Three Types Of Ospf Routers?

    Answer :

    ABR, internal router, and ASBR.

69. Question 69. What Are The Six Ospf Route Types?

    Answer :

    Intra-area, inter area, El, E2, Nl, and N2.

70. Question 70. Where Can Routes Be Summarized In An Ospf Network?

    Answer :

    OSPF routes are summarized on an ABR. External routes are summarized on an ASBR.

71. Question 71. How Is The Ospf Router Id Determined?

    Answer :

    If physical interfaces are only used, the OSPF router id is the highest IP address assigned to an active physical interface. If loopback interfaces are used, the OSPF router ID is the highest IP address assigned to a loopback interface. If the router-id command is used with the OSPF configuration, the address used with this command will be the router id.

72. Question 72. How Does Ospf Determine The Dr On A Multi-access Network?

    Answer :

    The router with the highest interface priority will be the router ID. If all the interface priorities on the multi-access network are the same, the router with the highest router ID will be the DR.

73. Question 73. How Does Ospf Determine An Inter Area Shortest Path?

    Answer :

    • First, calculate the shortest path to an ABR.
    • Second, calculate the shortest path across area 0 to an ABR that is attached to the destination area.
    • Third, calculate the shortest path across the destination area from the ABR to the destination network.

74. Question 74. What Is The Purpose Of An Ospf Virtual Link?

    Answer :

    To connect a nonzero area to the backbone if the nonzero area becomes disconnected from the backbone. A virtual link can also be used if the backbone, or area 0, becomes discontiguous.

75. Question 75. How Is The Ospf Cost Of An Interface Calculated?

    Answer :

    By default, the cost of an OSPF interface is 1 OO,OOO,OOO/(Interface Bandwidth). The constant 100,000,000 can be changed using the auto-cost reference-bandwidth command.

76. Question 76. Why Are Intra-area Summary Routes Not Allowed?

    Answer :

    OSPF databases on routers in the same area must be identical. If route summarization was allowed within an area, some routers would have specific routes and some routers would have summary routes for routers in the area. If this were allowed, the databases for the area would never agree.

77. Question 77. What Is The Range Of Host Addresses For Network 172.16.53.96/27?

    Answer :

    172.16.53.97 through 172.16.53.126.

78. Question 78. How Many Two-host Subnets Can Be Made From A /24 Network?

    Answer :

    64 because 2 bits are needed for the hosts on the network, leaving 6 bits for the subnet.

79. Question 79. What Is The Full Ipv6 Address Represented By Ff02::130f:5?

    Answer :

    FF02:0000:0000:0000:0000:0000: 130F:0005 

80. Question 80. Explain The Difference Between A Classful And A Classless Routing Protocol?

    Answer :

    Classless routing protocols advertise subnet mask information along with the network prefixes. Classful routing protocols do not. Therefore, for a c1assful protocol, all subnets for the major network number being used must be the same length. Also, c1assful protocol cannot support discontiguous networks prefixes.

81. Question 81. What Are The States That An Eigrp Route Can Be In And What Do These States Mean?

    Answer :

    The passive state means that a router has a successor for a route. The active state means that a router does not have a successor or feasible successor for a route and is actively sending queries to neighbors to get information about the route.

82. Question 82. Explain The Relationship Between Reported Distance And Feasible Distance And How They Determine Successors And Feasible Successors?

    Answer :

    The reported distance to a route that is sent to another router is the feasible distance on the reporting router. Feasible distance is the reported distance plus the metric between the receiving and reporting routers. The route with the lowest feasible distance is the successor. Any routes with a reported distance that is less than the feasible distance are feasible successors.

83. Question 83. What Are The Purposes Of Areas In An Ospf Network?

    Answer :

    Areas allow the design of a hierarchical network. Routes can be summarized or blocked in an area to reduce the amount of routing information on internal OSPF routers.

84. Question 84. What Is The Purpose Of A Default Route ?

    Answer :

    A default route is used if there is not a specific entry in the routing table for the destination.

85. Question 85. Describe The Difference Between Routing And Switching?

    Answer :

    Routing moves a letter or telephone call to the access layer.

    Switching makes the final delivery. A switching decision is made on the part of the address that is not used in routing.

Topic: Ccnp Routing Interview Questions
Interview Quesions on Ccnp Routing