Ccna certification Practice Tests

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 27.  C.  The routing protocol with the lowest administrative distance (AD) is always chosen. 

Within that protocol, if there are multiple routes to the same network, then the lowest 

metric is chosen. The route is chosen with the lowest administrative distance, not the 

highest administrative distance. The route with the lowest metric will be selected as the 

best route, but only when within the same routing protocol. The route with the highest 

metric will not be selected as the best route.

 28.  C.  EIGRP metrics are bandwidth, delay, load, reliability, and MTU, while RIP is a 

distance-vector protocol and only takes hop count into consideration for the metric. 

BGP is not suited for optimal performance since a large amount of resources need to be 

dedicated for the protocol.

 29.  A.  Cisco uses a metric for OSPF that is calculated as 10

8

/bandwidth. This cost value is of 

100 Mb/s (reference bandwidth) divided by the interface bandwidth. Delay, bandwidth, 

reliability, and load are used as a composite metric with EIGRP. K metrics are used to 

weight the calculation of the composite metric used with EIGRP. Bandwidth is used by 

OSPF, but only when used with the formula of 10

8

/bandwidth.

 30.  A.  It identifies the administrative distance (AD) of 110 for OSPF. The cost 

calculation is the reference bandwidth of 100 Mb/s divided by the link bandwidth. 

This calculation would result in a cost of 1. The calculation of the OSPF metric is 

10

8

/bandwidth, or 100,000,000/bandwidth. Therefore, a metric of 1 would equal 

100,000,000/100,000,000, and all of the other answers are wrong.

 31.  C.  The destination address of 0.0.0.0/0 is a special route called the default route or 

gateway of last resort. The 0.0.0.0/0 addresses are all hosts, and if a specific route is not 

matched in the routing table, then this route is the last resort. IOS and IOS-XR have local 

host routes; the routes provide a local routing path to an interface or internally configured 

IP address. Dynamic routes are routes that have been discovered by a dynamic routing 

protocol. There is no such thing as a loopback route.

 32.  B.  ICMP notifies the sending host if there is no viable route to the destination. The ICMP 

message sent to the sending host is a destination unreachable message. ICMP is not used 

to populate routing tables. ICMP does not maintain the routing table; dynamic routing 

protocols populate and maintain the routing table. ICMP is used to diagnose problems 

with an internetwork, but ICMP does not continuously diagnosis network paths.

 33.  B.  When a route table contains overlapping destination prefixes such as 192.168.0.0/16 

and 192.168.1.0/24, the route with the longest matching prefix is selected. The cost is not 

a consideration unless there are two routes with the same prefix length; then metrics are 

taken into consideration. The administrative distance (AD) is not a factor in deciding the 

destination path to be taken unless the routes have equal length prefixes with different 

route sources.

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