Interview Questions.

Question 1. What Is Routing?

Answer :

Routing is the procedure wherein items are forwarded from one vicinity to some other. Routing is a hop-by-hop paradigm.

A Cisco router plays routing and switching capabilities. Describe what every characteristic does.

Routing is a way to learn and keep recognition of the community topology. Each router keeps a routing table wherein it seems up the destination Layer 3 deal with to get the packet one step in the direction of its vacation spot.

The switching function is the real motion of transient site visitors via the router, from an inbound interface to an outbound interface.

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

Answer :

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

Networking Interview Questions
Question three. What Is The Difference Between Static And Dynamic Routes?

Answer :

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

Question 4. What Is A Default Route?

Answer :

Also called the gateway of closing resort, a default path is a unique kind of static route with an all-zeros community and network mask. The default route is used to direction any packets to a network that a router does no longer directly recognize about to a subsequent-hop router. By default, if a router receives a packet to a vacation spot network that isn't in its routing desk, it drops the packet. When a default course is designated, the router does no longer drop the packet. Instead, it forwards the packet to the IP deal with unique within the default course.

Networking Tutorial
Question 5. What Is A Routing Protocol?

Answer :

A Routing protocol defines the set of policies used by a router when it communicates with neighboring routers. Routing protocols listens for packets from different contributors in order to analyze and preserve a routing table.

CCNA Interview Questions
Question 6. What Is Administrative Distance?

Answer :

Administrative distance (AD) is an integer from zero to 255 that charges the trustworthiness of routing data acquired on a router from a neighboring router. The AD is used as the tiebreaker whilst a router has a couple of paths from specific routing protocols to the identical destination. The path with the decrease AD is the one given priority.

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

Answer :

Distance vector
Link-kingdom
Balanced hybrid
CCNP Interview Questions
Question eight. What Is The Ad For Each Of The Following?

Answer :

Directly connected interface 0
Static course 1
EIGRP ninety
IGRP 100
OSPF 110
RIP 120
External EIGRP a hundred and seventy
Unknown 255
Question nine. How Do Distance Vector Routing Protocols Function?

Answer :

Also called Bellman-Ford-Fulkerson algorithms, distance vector routing protocols bypass whole routing tables to neighboring routers. Neighboring routers then combine the acquired routing desk with their own routing table. Each router receives a routing table from its immediately linked neighbor. Distance vector routing tables include information about the overall fee and the logical cope with of the primary router on the direction to every network they know about.

CWNA (Certified Wireless Network Administrator) Interview Questions
Question 10. How Do Distance Vector Routing Protocols Keep Track Of Any Changes To The Internetwork?

Answer :

Distance vector routing protocols preserve music of an internetwork with the aid of periodically broadcasting updates out all lively interfaces. This broadcast includes the complete routing desk. This technique is regularly known as routing with the aid of rumor. Slow convergence of distance vector routing protocols can reason inconsistent routing tables and routing loops.

Question eleven. What Is Split Horizon?

Answer :

The rule of split horizon is that it's miles never useful to send data about a direction back within the course from which the original update came.

Network Administrator Interview Questions
Question 12. What Is Convergence?

Answer :

Convergence is whilst all routers have consistent expertise and correct routing tables.

Networking Interview Questions
Question thirteen. What Is Route Poisoning?

Answer :

With path poisoning, when a distance vector routing protocol notices that a course is not valid, the direction is marketed with an countless metric, signifying that the route is horrific. In RIP, a metric of 16 is used to signify infinity. Route poisoning is used with holddowns.

Question 14. What Are Hold-down Timers?

Answer :

Hold-down timers prevent regular update messages from reinstating a course that could have long gone terrible. Hold-down timers additionally tell routers to keep for a period of time any modifications that might have an effect on routes.

Question 15. What Are Triggered Updates?

Answer :

When a router notices that a directly linked subnet has changed state, it at once sends any other routing replace out its different interfaces as opposed to looking forward to the routing update timer to expire. Triggered updates are also referred to as Flash updates.

Border Gateway Protocol (BGP) Interview Questions
Question 16. What Is Ip Rip?

Answer :

IP RIP is a real distance vector routing protocol that sends its complete routing table out all lively interfaces every 30 seconds. IP RIP uses a hop count as its metric to determine the great route to a far flung community. The most allowable hop count is 15, which means that sixteen is unreachable. There are  versions of RIP. Version 1 is classful, and model 2 is classless. IP RIP can load-stability over as many as six identical-price paths.

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

Answer :

Here are the 4 timers that IP RIP uses to alter its performance:

Route replace timer Time among router updates. The default is 30 seconds.
Route invalid timer Time that ought to expire before a path becomes invalid. The default is one hundred eighty seconds.
Route keep-down timer If IP RIP gets an update with a hop count better than the metric recorded within the routing table, the router is going into holddown for 180 seconds.
Route flush timer Time from while a course turns into invalid to when it's far eliminated from the routing table. The default is 240 seconds.
Enhanced Interior Gateway Routing Protocol (EIGRP) Interview Questions
Question 18. How Do You Stop Rip Updates From Propagating Out An Interface On A Router?

Answer :

Sometimes you do not need RIP updates to propagate throughout the WAN, losing valuable bandwidth or giving out valuable statistics about your internetwork. The simplest manner to prevent RIP updates from propagating out an interface is to use the passive-interface worldwide configuration command.

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

Answer :

The display ip path command shows the Cisco routing desk’s contents.

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 number of a hundred hops, with a most hop count number of 255. IGRP uses bandwidth and line put off as its default metric, but it is able to also use reliability, load, and MTU.

Cisco Network Engineer Interview Questions
Question 21. How Do You Enable Igrp On A Cisco Router?

Answer :

The manner you permit IGRP on a Cisco router is just like the way you permit RIP, besides you specify IGRP because the protocol and upload an autonomous system wide variety.

For instance: RouterA(config)#router igrp 10 (10 is the AS quantity)

RouterA(config-router)#network 192.168.Zero.Zero

RouterA(config-router)#community 192.168.1.Zero

RouterA(config-router)#network 192.168.2.0

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

Answer :

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

Route update timer Time between router updates The default is ninety seconds.
Route invalid timer Time that should expire earlier than a route will become invalid . The default is 270 seconds.
Route keep-down timer If a vacation spot becomes unreachable, or if the following-hop router increases the metric recording in the routing desk, the router goes into holddown for 280 seconds.
Route flush timer[md]Time from when a direction becomes invalid to while it's far eliminated from the routing table. The default is 630 seconds.
Question 23. What Are Broadcast Domains?

Answer :

A broadcast area defines a group of devices that obtain each others’ broadcast messages. As with collisions, the more announces that occur on the network, the slower your community can be. This is because every tool that receives a published should manner it to peer if the published is supposed for it.

Cisco Asa Firewall Interview Questions
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 greater collision domain names and fewer collisions. Routers are used to break up broadcast domains. They create greater broadcast domains and smaller broadcast areas.

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

Answer :

Each layer of the OSI version can speak only with the layer above it, underneath it, and parallel to it (a peer layer). For example, the presentation layer can speak with best the utility layer, consultation layer, and presentation layer on the system it's far speaking with. These layers communicate with each other the usage of protocol information gadgets (PDUs). These PDUs manipulate statistics this is delivered to the person records at each layer of the model. This information resides in fields called headers (the front of the data subject) and trailers (the quit of the facts subject).

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

Answer :

When EIGRP returns a stuck in active (SIA) message, it method that it has no longer acquired a respond to a query. An EIGRP neighbour (or neighbours) have no longer answered to the question for that route.
When the SIA takes place, the router clears the neighbour that did now not reply to the question.
Question 27. Why Do You Not See Ospf Neighbours As Full/dr Or Full/bdr On Serial Link?

Answer :

This is regular. On factor-to-factor and point-to-multipoint networks, there are not any specified routers (DRs) or backup special routers (BDRs).

CWNA (Certified Wireless Network Administrator) Interview Questions
Question 28. What Is Type-1 And Type-2 Lsas In Ospf?

Answer :

Type-1 LSAs are router LSAs and are generated by means of every router for the place to which the router belongs.
Type-2 LSAs are network LSAs and are generated by the DR and BDR.
Question 29. What Is Ospf Network Types?

Answer :

Broadcast, multi-get entry to networks: Ehternet, token ring. Single mode operation.
Point-to-point : T1 CAS, ISDN BRI/PRI, single operation mode, no DR/BDR.
Non-broadcast multi-get right of entry to(NBMA) networks: Frame realy, ATM, MPLS. Five modes of operation.
Question 30. Explain The Function Of A Rendezvous Point ?

Answer :

A RP is the point of interest for multicast traffic. Traffic is forward to the RP from multicast assets. The RP then forwards site visitors to multicast receivers.

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

Answer :

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

Question 32. Describe The Operation Of Anycast Rp?

Answer :

Two or more RPs are configured with the identical IP address. The IP addresses of the RPs are marketed the usage of a unicast IP routing protocol. Each multicast router chooses the closet RP. If an RP fails, the routers transfer to the subsequent nearest RP after the unicast ip routing protocol converges. The MSDP is used between RPs to trade active multicast source information.

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

Answer :

CGMP and IGMP Snooping.

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

Answer :

Multicast forwarding choices are based at the entries within the unicast IP routing table. Multicast is not depending on how the unicast IP routing desk became constructed; you cans use any dynamic indoors routing protocol, static routes, or a mixture of the 2.

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

Answer :

RIP model 1 and IGRP are classful protocols and do not advertise subnet masks information.

RIP model 2 has a restrained network diameter of 15 hops. EIGRP, OSPF, and IS-IS use computational extensive algorithms for determining a shortest direction. BGP is predicated on simple strategies for first-rate path selection and loop detection, and may handle the variety of network prefixes required for Internet routing.

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

Answer :

When a summary deal with is created with an IGP (EIGRP, OSPF, and IS-IS), the unique routes of the precis aren't advertised. BGP advertises the summary, and all the specific routes of the precis until they're particularly suppressed.

Border Gateway Protocol (BGP) Interview Questions
Question 37. Why Does Ibgp Require A Full Mesh?

Answer :

BGP makes use of the AS _PATH characteristic for loop detection. If a router sees its very own AS number in a BGP commercial, the advertisement is dropped. IBGP routers have the equal AS range so the AS range can't be used for loop detection. IBGP buddies will now not promote it prefixes found out from one IBGP neighbor to any other IBGP neighbor; consequently, a full mesh is required.

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

Answer :

Route reflector and confederation.

Question 39. What Is Synchronization?

Answer :

Synchronization is a property of IBGP. An IBGP router will now not be given a prefix received from an IBGP neighbor if the prefix isn't already within the IP routing table.

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

Answer :

BGP assessments the NEXT HOP characteristic to determine if the NEXT HOP is available or in the IP routing desk.

Enhanced Interior Gateway Routing Protocol (EIGRP) Interview Questions
Question 41. Name All The Ways For Installing A Prefix In The Bgp Routing Table?

Answer :

Using the community command to transfer a router from the IP routing desk to the BGP routing desk.
Redistributing routes from the IP routing desk to the BGP routing table .
Learned from a BGP neighbor.
Question forty two. What Is The Order Of Preference For The Bgp Attributes As_path, Local_pref, Med, And Weight?

Answer :

WEIGHT, LOACL_PREF, AS_PATH, MED

Cisco Network Engineer Interview Questions
Question forty three. What Is The Purpose Of The Metric Or Multi_exit_disc Attribute?

Answer :

MED is used to select a direction into an self sustaining machine. A decrease MED price is desired.

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

Answer :

The LOCAL _PREF characteristic is marketed in the course of the independent device.

Question forty five. What Is The Purpose Of The Local_pref Attribute?

Answer :

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

Question forty six. What Is The Scope Of The Weight Attribute?

Answer :

WEIGHT has handiest local significance and isn't advertised to BGP peers.

Question forty seven. What Is The Purpose Of The Weight Attribute?

Answer :

If a router has a couple of path to the equal IP prefix, the exceptional direction is the one with the best WEIGHT value.

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

Answer :

If a router has multiple course to the identical IP prefix, the great path is the one with the shortest AS _PATH (assuming different BGP attributes are same).

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

Answer :

IBGP is the protocol used among routers within the same independent gadget. EBGP is the protocol used between routers in exceptional self reliant structures.
IBGP routes need to be synchronized before they may be transferred to the IP routing desk (except synchronization is disabled).
EBGP sets the next hop characteristic to the IP deal with of the interface used to communicate with the EBGP peer. The next hop characteristic is not modified while an IBGProuter advertises a prefix to an IBGP peer if the prefix turned into learned from an EBGP neighbor.
EBGP advertises all prefixes learned from an EBGP neighbor to all different EBGP associates. IBGP routers do not advertise prefixes found out from one IBGP neighbor to every other IBGP neighbor
Question 50. How Many Ospf Databases Are On An Ospf Router?

Answer :

The range of OSPF databases on a router is equal to the number of OSPF regions configured at the router.

Question fifty one. What Is The Administrative Distance Of Ospf Routes?

Answer :

a hundred and ten

Question fifty two. 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 ninety
IGRP has an administrative distance of one hundred.
OSPF has an administrative distance of one hundred ten.
RIP has an administrative distance of 120.
Therefore, the EIGRP route is desired.
Question fifty three. Describe The Structure And Format Of An Nsap Address?

Answer :

An NSAP cope with has a duration of8 to twenty bytes and includes three additives:

One to thirteen byte location identity

Six byte system identity

One byte NSAP selector that is always equal to 0 for a router

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

Answer :

OSPF has a spine place or area O. All nonzero regions have to be connected to the spine via a router or a virtual hyperlink. IS-IS has a spine vicinity made up ofa contiguous chain of Level 2 capable routers.

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

Answer :

Level 1 routing is routing among locations inside the equal IS-IS location.

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

Answer :

Intra-region routing.

Question fifty seven. 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 inside the router's configured vicinity. The Level 2 database is used to direction between destinations in special areas.

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

Answer :

An Area Border Router (ABR).

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 region OSPF routes and external routes which have been injected into OSPF. By default, IS-IS does no longer market it inter vicinity or external routes into a place, however injects a default direction.

Question 60. What Is Route Leaking?

Answer :

Redistribution of Level 2 routes into a place as Level l routes.

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 ten. Therefore, the EIGRP route is favored.

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 route metric. A extensive metric uses 24 bits for the interface metric and 32 bits for the route metric.

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

Answer :

OSPF intra-location and inter region routes, and a default direction. External routes aren't advertised into a stub area.

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

Answer :

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

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

Answer :

OSPF intra-vicinity and inter region routes, and in all likelihood a default course. External routes from ABRs are blocked, and outside routes from ASBRs are transformed to Nl or N2 routes.

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

Answer :

OSPF intra-region routes and a default course. External routes from ABRs are blocked, and outside routes from ASBRs are converted to Nl or N2 routes.

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

Answer :

An El route carries the OSPF price to attain the ASBR plus the price from the ASBR to the external course. An E2 route incorporates most effective the fee from the ASBR to the external course.

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

Answer :

ABR, inner router, and ASBR.

Question 69. What Are The Six Ospf Route Types?

Answer :

Intra-place, inter vicinity, El, E2, Nl, and N2.

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.

Question 71. How Is The Ospf Router Id Determined?

Answer :

If physical interfaces are most effective used, the OSPF router id is the best IP address assigned to an lively physical interface. If loopback interfaces are used, the OSPF router ID is the highest IP deal with assigned to a loopback interface. If the router-identity command is used with the OSPF configuration, the cope with used with this command will be the router identification.

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

Answer :

The router with the best interface precedence might be the router ID. If all of the interface priorities at the multi-access network are the identical, the router with the highest router ID will be the DR.

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

Answer :

First, calculate the shortest course to an ABR.
Second, calculate the shortest direction throughout region 0 to an ABR this is connected to the destination vicinity.
Third, calculate the shortest route throughout the destination area from the ABR to the destination network.
Question 74. What Is The Purpose Of An Ospf Virtual Link?

Answer :

To join a nonzero location to the spine if the nonzero location turns into disconnected from the spine. A digital hyperlink can also be used if the spine, or area zero, will become discontiguous.

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

Answer :

By default, the fee of an OSPF interface is 1 OO,OOO,OOO/(Interface Bandwidth). The consistent one hundred,000,000 can be changed the use of the automobile-fee reference-bandwidth command.

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

Answer :

OSPF databases on routers in the identical location need to be equal. If route summarization become allowed within an area, some routers could have particular routes and some routers would have summary routes for routers within the region. If this have been allowed, the databases for the location could in no way agree.

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

Answer :

172.16.Fifty three.Ninety seven through 172.Sixteen.53.126.

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

Answer :

64 due to the fact 2 bits are wished for the hosts at the community, leaving 6 bits for the subnet.

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

Answer :

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

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

Answer :

Classless routing protocols advertise subnet mask records in conjunction with the community prefixes. Classful routing protocols do now not. Therefore, for a c1assful protocol, all subnets for the primary network wide variety getting used should be the same duration. Also, c1assful protocol can not guide discontiguous networks prefixes.

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

Answer :

The passive nation approach that a router has a successor for a course. The active kingdom way that a router does no longer have a successor or feasible successor for a path and is actively sending queries to acquaintances to get records about the direction.

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

Answer :

The pronounced distance to a path that is despatched to another router is the viable distance on the reporting router. Feasible distance is the mentioned distance plus the metric among the receiving and reporting routers. The route with the lowest viable distance is the successor. Any routes with a mentioned distance this is less than the viable distance are possible successors.

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

Answer :

Areas permit the design of a hierarchical community. Routes may be summarized or blocked in an area to lessen the amount of routing information on inner OSPF routers.

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

Answer :

A default route is used if there is not a specific entry within the routing table for the vacation spot.

Question eighty five. Describe The Difference Between Routing And Switching?

Answer :

Routing moves a letter or phone name to the get admission to layer.

Switching makes the final transport. A switching choice is made on the part of the deal with that isn't utilized in routing.