Question 1. Does Eigrp Support Secondary Addresses?
EIGRP does guide secondary deal with. Since EIGRP assets information packets from the primary addresses, Cisco recommends that we configure all routers on a specific subnet with primary addresses that belong to the similar subnet. Routers don’t shape EIGRP friends over secondary community. For which, if all the primary IP addresses of routers don’t agree, issues arises with neighbor adjacency.
Question 2. What Does The Eigrp Stuck In Active Message Mean?
When EIGRP returns a caught in energetic message, because of this it has no longer acquired a reply from a query. It sends a query when a route is misplaced and any other possible direction does now not exist in the topology desk. The SIA is caused by 2 sequential occasions:
The reported course via the SIA has gone away.
An EIGRP neighbor (or friends) have not replied to the question for that direction.
When the SIA takes place, the router clears the neighbor that did now not reply for the query. When it occurs, determine which neighbor has been cleared. We have to Keep in thoughts that this router can be many hops away.
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Question 3. What Does The Neighbor Statement In The Eigrp Configuration Section Do?
The neighbor command is used in EIGRP which will outline a neighboring router with which to trade facts of routing. Because of the modern behavior of the command, EIGRP exchanges facts of routing with the friends inside the shape of unicast packets every time the neighbor command is configured for interface. EIGRP holds on processing all multicast packets that come inbound on that interface. EIGRP also mutes sending multicast packets on that interface.
The perfect behavior of this command is for EIGRP to begin sending EIGRP packets as unicast packets to the required neighbor, however don’t prevent sending and receiving multicast packets on that interface. As the command does not behave as meant, the neighbor command ought to used cautiously.
Question 4. Why Does The Eigrp Passive-interface Command Remove All Neighbors For An Interface?
The passive interface command disables the transmission and receipt of EIGRP hey packets on interface. Not in addition IGRP or RIP, EIGRP sends hiya packets so one can form and maintain neighbor adjacency. Not having a neighbor adjacency, EIGRP doesn’t trade routes with a neighbor. For which the passive interface command prevents the change of routes on the interface. Although EIGRP does not obtain or ship routing updates on an interface configured with the passive interface command, it includes the deal with of the interface in routing updates sent out of different non-passive interfaces.
Question 5. What Is The Difference In Metric Calculation Between Eigrp And Igrp?
The EIGRP metric is obtained when you multiply the IGRP metric of 256. The IGRP uses handiest 24 bits in its replace packet for the metric field, but 32 bit is utilized by EIGRP in its replace packet for the metric discipline. E.G the IGRP metric to a vacation spot network is 8586, however the EIGRP metric might be 8586 x 256 = 2,198,016. Integer division is used when we divide 10^7 by using lowest BW, so the calculation involves division of integer, which might also leads to a version from guide calculation.
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Question 6. How Does Eigrp Behave Over A Gre Tunnel Compared To A Directly Connected Network?
EIGRP will use the equal administrative distance and metric calculation to the GRE tunnel. The calculation of cost is based on delay and bandwidth. The bandwidth and delay of the GRE tunnel should be taken from the tunnel interface configured on the router. The tunnel could be dealt with like a without delay linked network.
If there are 2 paths to reach a n/w both through a tunnel interface or VLAN interface, EIGRP prefers the Virtual-Access Interface VLAN interface due to the fact the VLAN interface has more bandwidth than the tunnel interface. To have an effect on the routing via the tunnel interface, It increases the bandwidth parameter of the tunnel interface, or will increase the delay parameter of the VLAN interface.
Question 7. Can An Ospf Default Be Originated Into The System Based On External Information On A Router That Does Not Itself Have A Default?
OSPF generates a default simplest if it's far configured using the command default-statistics originate and if there is a default community inside the field from a specific method. In OSPF the default path is 0.Zero.0.Zero. If we want an OSPF enabled router to generate a default course even though it does now not have a default path, use the command default-information originate continually.
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Question 8. How Does Cisco Accommodate Ospf Routing On Partial-mesh Frame Relay Networks?
We can configure OSPF to apprehend whether it have to try to use multicast facilities on a multi-get right of entry to interface. If multicast is to be had, OSPF normally makes use of it for its everyday multicasts
Cisco IOS Software Release 10.Zero includes a function called sub-interfaces. We can use sub interfaces with Frame Relay to tie together a fixed of digital circuits to shape a virtual interface, it acts as a unmarried IP subnet. All structures inside the sub-internet need to be completely meshed.
Question nine. Which Address-wild-masks Pair Should I Use For Assigning An Unnumbered Interface To An Area?
When we configured an unnumbered interface, it references an any other interface on the router. When we allow OSPF on the unnumbered interface, we ought to use the deal with-wild-mask pair of interfaces to which the unnumbered interface is pointing.
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Question 10. What Is The Link-country Re-transmit Interval, And What Is The Command To Set It?
OSPF sends acknowledgment of every newly received link-nation advertisement. It does this by way of sending LSA packets. After that LSAs are re-transmitted till they're recounted. The hyperlink kingdom while re-transmit the c language it defines the time among the re-transmissions. We can use the command IP OSPF re-transmit c language to set the re-transmit c program languageperiod. Five seconds is the default value.
Question 11. Does Eigrp Require An Ip Default-network Command To Propagate A Default Route?
Although EIGRP can propagate a default path the usage of the default community approach, it isn't always required. EIGRP redistributes default routes without delay.
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Question 12. Should I Always Use The Eigrp Log-neighbor-adjustments Command When I Configure Eigrp?
Yes, this command makes it clean to determine why an EIGRP neighbor was reset. This reduces troubleshooting time.
Switching Interview Questions
Question 13. What Debugging Capabilities Does Eigrp Have?
There are protocol-impartial and -dependent debug commands. There is also a suite of show instructions that display neighbor desk status, topology desk repute, and EIGRP traffic statistics. Some of those commands are:
show ip eigrp buddies
display ip eigrp interfaces
display ip eigrp topology
show ip eigrp site visitors
Question 14. What Does The Word Serno Mean On The End Of An Eigrp Topology Entry When You Issue The Show Ip Eigrp Topology Command?
show ip eigrp topology
P 172.22.71.208/29, 2 successors, FD is 46163456
via 172.30.1.Forty two (46163456/45651456), Serial0.2, serno 7539273
through 172.30.2.49 (46163456/45651456), Serial2.6, serno 7539266
Serno stands for serial variety. When DRDBs are threaded to be sent, they're assigned a serial variety. If you display the topology desk on the time an access is threaded, it shows you the serial range associated with the DRDB.
Threading is the method used inside the router to queue items up for transmission to friends. The updates are not created till it is time for them to go out the interface. Before that, a linked listing of suggestions to objects to send is created (for instance, the thread).
These sernos are neighborhood to the router and are not handed with the routing replace.
Question 15. What Percent Of Bandwidth And Processor Resources Does Eigrp Use?
EIGRP version 1 brought a characteristic that prevents any unmarried EIGRP process from the usage of extra than fifty percentage of the configured bandwidth on any link at some stage in intervals of network convergence. Each AS or protocol (as an example, IP, IPX, or Appletalk) serviced through EIGRP is a separate process. You can use the ip bandwidth-percent eigrp interface configuration command so as to properly configure the bandwidth percent on every WAN interface. Refer to the EIGRP White Paper for extra records on how this selection works.
In addition, the implementation of partial and incremental updates approach that EIGRP sends routing statistics handiest when a topology exchange takes place. This characteristic extensively reduces bandwidth use.
The viable successor function of EIGRP reduces the quantity of processor sources used by an self sustaining device (AS). It calls for only the routers tormented by a topology exchange to perform course re-computation. The course re-computation simplest occurs for routes that have been affected, which reduces search time in complex statistics structures.
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Question 16. Does Eigrp Support Aggregation And Variable Length Subnet Masks?
Yes, EIGRP supports aggregation and variable duration subnet mask (VLSM). Unlike Open Shortest Path First (OSPF), EIGRP lets in summarization and aggregation at any factor inside the community. EIGRP helps aggregation to any bit. This permits well designed EIGRP networks to scale rather nicely without using areas. EIGRP also helps automatic summarization of network addresses at major network borders.
Question 17. Does Eigrp Support Areas?
No, a single EIGRP method is analogous to an area of a link-country protocol. However, in the system, records may be filtered and aggregated at any interface boundary. In order to certain the propagation of routing data, you could use summarization to create a hierarchy.
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Question 18. Can I Configure More Than One Eigrp Autonomous System On The Same Router?
Yes, you can configure more than one EIGRP independent device on the same router. This is typically carried out at a redistribution point where EIGRP independent systems are interconnected. Individual router interfaces have to handiest be covered within a single EIGRP self reliant system.
Cisco does no longer endorse going for walks more than one EIGRP self sustaining structures at the same set of interfaces at the router. If a couple of EIGRP autonomous systems are used with a couple of points of mutual redistribution, it is able to motive discrepancies in the EIGRP topology table if correct filtering isn't carried out at the redistribution points. If possible, Cisco recommends you configure best one EIGRP independent machine in any single self sustaining gadget. You can also use any other protocol, which includes Border Gateway Protocol (BGP), for you to join the two EIGRP independent systems.
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Question 19. If There Are Two Eigrp Processes That Run And Two Equal Paths Are Learned, One By Each Eigrp Process, Do Both Routes Get Installed?
No, only one direction is hooked up. The router installs the route that was discovered thru the EIGRP procedure with the lower Autonomous System (AS) range. In Cisco IOS Software Releases in advance than 12.2(7)T, the router set up the path with the present day timestamp obtained from either of the EIGRP processes. The trade in behavior is tracked with the aid of Cisco trojan horse ID CSCdm47037.
Question 20. Why Are Routes Received From One Neighbor On A Point-to-multipoint Interface That Runs Eigrp Not Propagated To Another Neighbor On The Same Point-to-multipoint Interface?
The split horizon rule prohibits a router from advertising a direction via an interface that the router itself makes use of to attain the destination. In order to disable the break up horizon conduct, use the no ip break up-horizon eigrp as-quantity interface command. Some important factors to don't forget approximately EIGRP split horizon are:
Split horizon conduct is turned on through default.
When you exchange the EIGRP cut up horizon placing on an interface, it resets all adjacencies with EIGRP neighbors accessible over that interface.
Split horizon must handiest be disabled on a hub website online in a hub-and-spoke community.
Disabling cut up horizon on the spokes considerably increases EIGRP reminiscence intake at the hub router, in addition to the amount of site visitors generated at the spoke routers.
The EIGRP cut up horizon conduct isn't controlled or motivated by means of the ip split-horizon command.
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Question 21. When I Configure Eigrp, How Can I Configure A Network Statement With A Mask?
The non-compulsory community-mask argument turned into first brought to the community announcement in Cisco IOS Software Release 12.Zero(4)T. The masks argument can be configured in any format (along with in a community mask or in wild card bits). For instance, you may use community 10.10.10.Zero 255.255.255.252 or community 10.10.10.Zero zero.0.Zero.Three.
Question 22. I Have Two Routes: 172.16.1.Zero/24 And 172.Sixteen.1.Zero/28. How Can I Deny 172.16.1.Zero/28 While I Allow 172.16.1.0/24 In Eigrp?
In order to try this you need to apply a prefix-list, as proven right here:
router eigrp 100
distribute-list prefix take a look at in
no eigrp log-neighbor-adjustments
Ip prefix-list test seq 5 permit 172.16.1.0/24
This permits handiest the 172.Sixteen.1.Zero/24 prefix and therefore denies 172.16.1.0/28.
Note: The use of ACL and distribute-list underneath EIGRP does no longer paintings in this example. This is because ACLs do now not test the masks, they just check the network element. Since the network portion is the identical, when you permit 172.16.1.Zero/24, you also allow 172.16.1.Zero/28.
Question 23. I Have A Router That Runs Cisco Express Forwarding (cef) And Eigrp. Who Does Load-balancing When There Are Multiple Links To A Destination?
The manner wherein CEF works is that CEF does the switching of the packet based totally at the routing desk that is populated via the routing protocols consisting of EIGRP. In quick, CEF does the weight-balancing once the routing protocol table is calculated.
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Question 24. How Can I Use Only One Path When A Router Has Two Equal Cost Paths?
Configure the bandwidth fee at the interfaces to default, and increase the delay on the backup interface in order that the router does not see identical cost paths.
Routing Protcol Interview Questions
Question 25. What Is The Eigrp Stub Routing Feature?
The Stub routing feature is used to conserve bandwidth by summarizing and filtering routes. Only designated routes are propagated from the far off (Stub) router to the distribution router due to the Stub routing function. For greater facts about the Stub routing characteristic, check with EIGRP Stub Routing. The EIGRP stub function can be configured on the transfer with the eigrp stub [receive-only] [leak-map name] [connected] [static] [summary] [redistributed] command. This feature may be eliminated with the no eigrp stub command. When you eliminate the eigrp stub command from the transfer, the transfer that runs the IP Base picture throws this mistake:
EIGRP is limited to stub configurations most effective
Question 26. How Can I Send A Default Route To The Stub Router From The Hub?
Do this underneath the outbound interface on the hub router with the ip precis-cope with eigrp X 0.Zero.Zero.Zero 0.Zero.Zero.0 command. This command suppresses all the greater unique routes and handiest sends the summary course. In the case of the 0.0.Zero.Zero zero.Zero.Zero.Zero, it method it suppresses the whole thing, and the handiest path this is within the outbound update is zero.0.Zero.0/0. One downside to this method is that EIGRP installs a 0.Zero.Zero.Zero/zero direction to Null0 is the nearby routing desk with an admin distance of five.
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Question 27. What Are Different Route Types In Eigrp?
There are 3 exclusive styles of routes in EIGRP:
Internal Route—Routes which might be originated within the Autonomous System (AS).
Summary Route—Routes which can be summarized inside the router (as an instance, internal paths which have been summarized).
External Route—Routes that are redistributed to EIGRP.
Cisco Interview Questions
Question 28. How Do You Redistribute An Ipv6 Default Route In Eigrp?
For redistributing an IPv6 default direction in EIGRP, a sample configuration is shown here:
ipv6 prefix-list DEFAULT-ONLY-V6 seq 10 permit ::/zero
course-map DEFAULT_2EIGRP-V6 permit 10
match ipv6 deal with prefix-list DEFAULT-ONLY-V6
router eigrp Starz_EIGRP
deal with-circle of relatives ipv6 unicast
redistribute static path-map DEFAULT_2EIGRP-V6
Question 29. What Is An Offset-listing, And How Is It Useful?
The offset-list is an function used to modify the composite metrics in EIGRP. The price configured within the offset-list command is added to the delay cost calculated through the router for the direction matched by means of an get right of entry to-listing. An offset-listing is the desired approach to persuade a specific route that is advertised and/or chosen.
Question 30. How Can I Tag External Routes In Eigrp?
You can tag routes that EIGRP has discovered from every other routing protocol using a 32 bit tag fee. Starting with ddts CSCdw22585, internal routes also can be tagged. However, the tag cost can not exceed 255 because of packet boundaries for inner routes.
Question 31. What Are The Primary Functions Of The Pdm?
EIGRP helps 3 protocol suites: IP, IPv6, and IPX. Each of them has its own PDM. These are the number one functions of PDM:
Maintaining the neighbor and topology tables of EIGRP routers that belong to that protocol suite
Building and translating protocol precise packets for DUAL
Interfacing DUAL to the protocol specific routing desk
Computing the metric and passing this information to DUAL; DUAL handles only the selecting of the possible successors (FSs)
Implement filtering and get right of entry to lists.
Perform redistribution functions to/from different routing protocols.
Question 32. What Are The Various Load-balancing Options Available In Eigrp?
The offset-listing can be used to modify the metrics of routes that EIGRP learns thru a particular interface, or PBR can be used.
Question 33. What Does The %twin-five-nbrchange: Ip-eigrp(0) 100: Neighbor 10.254.Zero.3 (tunnel0) Is Down: Holding Time Expired Error Message Mean?
This message indicates that the router has now not heard any EIGRP packets from the neighbor inside the keep-time restriction. Because this is a packet-loss trouble, take a look at for a Layer 2 hassle.
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Question 34. From The sixteen:29:14.262 Poison Squashed: 10.X.X.X/24 Reverse Message, What Does Poison Squashed Mean?
The router threads a topology table access as a poison in respond to an replace obtained (the router units up for poison opposite). While the router is constructing the packet that contains the poison opposite, the router realizes that it does now not want to ship it. For instance, if the router gets a question for the course from the neighbor, it is presently threaded to poison. Thus, it sends the poison squashed message.
Question 35. Is It Normal That Eigrp Takes Over 30 Seconds To Converge?
EIGRP taking longer to converge below heavy CPU utilization is a regular conduct. EIGRP convergence is faster whilst you lower the preserve time. The lowest values for hey and maintain time are 1 2d and 3 seconds respectively. For instance:
Router(Config)# interface Fa0/0
!--- (Under an interface without delay connected to EIGRP friends.)
Router(Config-if)#ip good day-interval eigrp 1
Router(Config-if)#ip preserve-time eigrp 3