Chapter 14


"Do I Know This Already?" Quiz


















a, b, c, d









Which command has superceded the passive-interface command for preventing EIGRP traffic from traversing a link?


The network network wildcard-mask suppresses Hellos between interfaces not included in the network command. This means that no routing updates can be sent or received on that interface.


What is the preferred configuration for a hybrid multipoint NBMA network when one VC has a CIR of 56 kbps and the other five VCs each have a CIR of 256 kbps?


The preferred configuration for a hybrid multipoint NBMA network, in which one circuit is lower than the other circuits, is to create a point-to-point subinterface for the lower circuit and then to configure the bandwidth to reflect the CIR of the link. Another subinterface should be created as a multipoint interface with a configured bandwidth that equals the aggregate CIR of all the circuitsin this instance, 5 * 256 kbps, or 1280 kbps. An alternative solution is to configure each PVC as a point-to-point link.


With four Frame Relay circuits in a multipoint solution and a bandwidth configuration of 224, what is the EIGRP bandwidth allocation per circuit, and where would the bandwidth command be configured?


The command would be configured on the physical interface. The CIR of each circuit is 56 kbps.


Explain the purpose of the command no auto-summary .


The command no auto-summary is used to turn off automatic summarization, which in EIGRP happens at the IANA or major network boundary. This command is used in conjunction with the interface commands for manual summarization.


Explain the meaning of the command ip bandwidth-percent eigrp 63 100 .


This command overrides the default bandwidth of 50 percent that is allocated to EIGRP for network overhead. This command sets the bandwidth allocation to be 100 percent of the link for the EIGRP autonomous system of 63 on the interface upon which it is configured. This command would be used if the bandwidth command had set the logical bandwidth of the link to be artificially low.


In what instances will EIGRP automatically redistribute?


EIGRP will automatically redistribute between other EIGRP processes with the same autonomous system. EIGRP will also redistribute between itself and IGRP as long as both processes are running the same autonomous system number.


How long is the holdtime, by default?


The holdtime is three times the Hello timer. The holdtime is 15 seconds or 180 seconds, depending on the medium.


For what is the variance command used?


The variance command is used to determine additional paths to be included in load balancing traffic to remote networks. The command is used in conjunction with the multiplier number. This number multiplies the path with the best ( lowest ) metric by the number stated as the multiplier. Any paths that the router knows of that have a metric value equal to or less than this value are included in the paths for load balancing. The amount of traffic sent across each path will be proportional to the metric value of the path.


What command is used to display the passive and active state of the routes?


The command show ip eigrp topology shows the passive and active state of the routes that are contained in the table. The route is passive if the route is operational; it is set in an active state if the router must query its neighbors for alternative paths to a network. This command also shows the number of successors and the neighbors and distance information.


What command is used in EIGRP to perform manual summarization?


The interface command ip summary-address autonomous-system-number address mask is used to define the summary address to be used.


For Frame Relay, when would you configure the physical interface (as opposed to a subinterface) with the bandwidth command?


If all the circuits have the same CIR, the bandwidth command can be used on the physical interface. The interface will divide the available bandwidth set on the command by the number of circuits.


Which command is used to display all types of EIGRP packets that are both received and sent by a router?


The command debug eigrp packet displays the types of EIGRP packets that are both sent and received by the router.


What problems can be solved with the configuration of summarization?


Summarization reduces the amount of resources needed by both the network and the routers within the network. The routing tables are reduced, which speeds up the lookup when forwarding data that is process switched. It also reduces the scope of the queries sent out by a router. If a router has no feasible successor, it queries its neighbor for an alternative route. If the neighbor has no route to offer, the query is forwarded on until a route is found or the search is exhausted. If summarization has been configured, the route that is being queried might have been summarized, and thus the query will end.


Why would you configure an EIGRP router as a stub router?


The stub configuration is typically used on small-capacity routers in a hub-and-spoke WAN environment. The router has no other neighbors and accesses the network through a distribution layer router. It is not necessary, therefore, for this remote router to have a complete routing table that might overwhelm its limited resources. The remote router needs only a default route to the distribution router that can serve all its needs.

Another reason to configure the remote router as a stub is to lend a hand to the rest of the network. If a query is sent to a remote router, the delays involved might result in the path being SIA. If the stub configuration has been configured, the router will immediately respond to queries as inaccessible.


Explain the parameters receive-only, connected, static , and summary used in the command eigrp stub .


Descriptions of the parameters are listed in the following table.

 router(config-router)#  eigrp stub [receive-only  connected  static  summary]  




(Optional) Sets the router as a receive-only neighbor


(Optional) Advertises connected routes


(Optional) Advertises static routes


(Optional) Advertises summary routes


When configuring the variance command, which routes can be used?


Any feasible successor in the topology table can be used in the variance command.


Give two reasons why you might wish to change the Hello timer.


The command ip hello-interval timer is typically used to decrease the time between Hellos to ensure that the network is more stable and converges more quickly. Although this increases the amount of bandwidth consumed, it is a minimal cost. It becomes very useful in the WANs, particularly when NBMA clouds are used. EIGRP treats both Frame Relay and SMDS as NBMA technologies, resulting in Hello timers that assume a low bandwidth medium (less than T1 speeds) and that set the timer to 60 seconds by default.


What should be considered in terms of EIGRP configuration when there are many VCs entering a WAN and no subinterfaces have been configured?


If the serial line has many VCs in a multipoint configuration, EIGRP will evenly distribute its overhead between the VCs, without the use of subinterfaces. The bandwidth command should therefore reflect the access link speed into the Frame Relay cloud. If the serial interface is accessing an NBMA environment such as Frame Relay, the situation is straightforward. Your company might have five VCs from your router's serial interface, each carrying 56 kbps. The access link will need a capacity of 5 * 56 kbps. Remember, the aggregate configured bandwidth cannot exceed the access speed of the interface.

If the multipoint network has differing speeds allocated to the VCs, a more complex solution is needed. You should take the lowest CIR and to simply multiply it by the number of circuits. This is applied to the physical interface. The problem with this configuration is that the higher-bandwidth links will be underutilized for some things.

Another solution is to configure many subinterfaces, each with a point-to-point link.


On what occasions should you consider configuring the bandwidth on subinterfaces?


If the multipoint network has differing speeds allocated to the VCs, it is much easier to configure and manage an environment that has used subinterfaces, where a VC is logically treated as if it were a separate interface or point-to-point. The bandwidth command can be configured on each subinterface, which allows different speeds on each VC. In this second solution, subinterfaces are configured for the links with the differing CIRs. The links that have the same configured CIR are presented as a single subinterface with a bandwidth, which reflects the aggregate CIR of all the circuits. Cisco recommends this as the preferred solution.

CCNP BSCI Exam Certification Guide
CCNP BSCI Exam Certification Guide (CCNP Self-Study, 642-801) (3rd Edition)
ISBN: 1587200856
EAN: 2147483647
Year: 2002
Pages: 194
Authors: Clare Gough © 2008-2017.
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