The Candid Test On CCNA Chapter 11

The default administrative distance for OSPF is 110. Administrative distance is a metric used by routers to determine the best path for forwarding network traffic. OSPF is a routing protocol that uses this metric to determine the best path within an autonomous system (AS). A lower administrative distance indicates a more preferred route. In the case of OSPF, a default administrative distance of 110 means that OSPF routes are preferred over routes from other routing protocols with higher administrative distances.

To prevent the dead time from reaching zero, hello packets must be received between neighbors. Hello packets are used by routing protocols to establish and maintain neighbor relationships. By exchanging hello packets, routers can periodically check the status and availability of their neighboring routers. This helps to ensure that the routers are still connected and functioning properly. If hello packets are not received within a certain time frame, the dead time will reach zero, indicating that the neighbor is no longer reachable.

OSPF uses bandwidth to calculate the cost to a destination network. The cost is determined based on the bandwidth of the links along the path to the destination. A higher bandwidth link will have a lower cost, indicating a faster and more efficient path. This allows OSPF to select the best path to a destination network based on the available bandwidth.

The correct answer is B(config-router)# network 192.168.1.0 0.0.0.3 area 0. This statement is used to enable OSPF on the interface connected to the 192.168.1.0 network with a wildcard mask of 0.0.0.3, which means that only the first two bits of the fourth octet will be considered for OSPF. This will include the IP addresses 192.168.1.0, 192.168.1.1, 192.168.1.2, and 192.168.1.3 in the OSPF routing process.

The command "network 192.168.0.0 0.0.15.255" in OSPF configuration specifies that the network 192.168.0.0/24 through 192.168.15.0/24 should be advertised in OSPF updates. The wildcard mask 0.0.15.255 indicates that the first 20 bits of the network address should match exactly, while the last 12 bits can be any value. Therefore, the range of networks advertised will include all subnets from 192.168.0.0/24 to 192.168.15.0/24.

The correct answer is a combination of three network commands. The first command "network 10.1.0.0 0.0.0.255 area 0" enables OSPF for any interface on R1 that falls within the range of 10.1.0.0 to 10.1.0.255. The second command "network 10.1.1.0 0.0.0.255 area 0" enables OSPF for any interface on R1 that falls within the range of 10.1.1.0 to 10.1.1.255. The third command "network 10.1.2.4 0.0.0.3 area 0" enables OSPF for any interface on R1 that falls within the range of 10.1.2.4 to 10.1.2.7. Together, these commands ensure that OSPF is enabled for all interfaces connected to the exhibited subnets.

The possible cause for the show ip ospf neighbor command revealing no neighbors is that the OSPF hello or dead timers do not match. OSPF neighbors establish and maintain adjacency by exchanging hello packets at regular intervals. If the hello or dead timers are not configured to match on Router1 and Router2, they will not be able to establish a neighbor relationship and therefore the show ip ospf neighbor command will not display any neighbors.

In OSPF, the cost metric is calculated based on the bandwidth of the interface. The higher the bandwidth, the lower the cost. Since the question does not provide any specific information about the bandwidth of the interface between JAX and the 10.0.0.0/24 network, we cannot determine the exact cost. However, we can conclude that JAX would put a cost of 1787 in its routing table for the 10.0.0.0/24 network.

After the router loses power and reboots, the configuration file is loaded but OSPF has not yet converged. This means that the SPF algorithm has not completed all calculations. As a result, no routes will be present in the routing table except for the directly connected networks that are operational. These directly connected networks will be the only ones that the router has immediate knowledge of, while it waits for OSPF to converge and update the routing table with all the routes for the entire network.

The configuration statements B(config)# router ospf 1 and B(config-router)# router-id 192.168.1.5 would give the results shown in the output of the show ip protocols command. These statements configure OSPF with process ID 1 and set the router ID to 192.168.1.5. The router ID is used to uniquely identify the router within the OSPF domain.

OSPF (Open Shortest Path First) uses designated routers to reduce the number of exchanges of routing information in networks with a large number of neighbors. The designated router is responsible for collecting and distributing routing information to all other routers within the network. By having a designated router, the other routers only need to exchange routing information with this designated router, rather than exchanging information with every other router in the network. This reduces the amount of routing information exchanges and helps to optimize network performance. The backup designated router is also utilized to provide redundancy in case the designated router fails.

When RouterD is added to the network, there is no immediate change in the OSPF DR/BDR (Designated Router/Backup Designated Router) election process. The election for DR/BDR only occurs when there is a change in the network or when the current DR/BDR goes down. Therefore, until either the current DR or BDR goes down, there will be no change in the DR or BDR.

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The correct answer is RouterB(config)# ip route 0.0.0.0 0.0.0.0 172.16.6.6 and RouterB(config)# router ospf 10 RouterB(config-router)# default-information originate. This command sequence configures RouterB to redistribute the default route (gateway of last resort) into OSPF area 0. The first command sets up the default route with the next hop IP address of 172.16.6.6. The second command enables RouterB to advertise this default route to other routers in OSPF area 0. By redistributing the default route, other routers in the OSPF network will be aware of the gateway of last resort and can use it to reach destinations outside of the OSPF domain.

The cost of the route to the 10.0.0.0 network is 1786.

Router B will play the role of DR (Designated Router) for network 192.168.1.200 and the role of BDR (Backup Designated Router) for network 192.168.1.204.

In an OSPF network, each router forms an adjacency with every other router in the network. Without a designated router (DR) or backup designated router (BDR) elected, each router will still form an adjacency with every other router. In the given exhibit, there are a total of 7 routers. To build the complete topology, each router must form an adjacency with the other 6 routers in the network. Therefore, the correct answer is 6.

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OSPF DR/BDR elections are used in broadcast multiaccess networks to select a designated router (DR) and a backup designated router (BDR) to reduce the amount of OSPF traffic and simplify the network. In these networks, all routers are connected to a common network segment, and the DR and BDR are responsible for exchanging OSPF information with other routers on behalf of the entire network. This ensures that only the DR and BDR need to maintain a full OSPF database, reducing the amount of OSPF traffic and processing power required by other routers. In NBMA networks, such as Frame Relay or X.25, elections are sometimes required if the network does not support multicast communication, and a designated router is needed to represent the network.

The fact that the highest router ID was most likely determined via an OSPF router-id statement or statements can be concluded from the given information. This is because the router with the highest router ID, which is router D, has been elected as the DR. This indicates that the router ID played a significant role in the DR/BDR election process.

The command "ip ospf priority 255" sets the OSPF priority of the interface fa0/0 on router A to the highest possible value. However, the priority of a router interface only affects the election of the DR and BDR if there is a tie in the OSPF router ID. Since the question states that all routers are running OSPF with default router IDs, the router with the highest router ID will always be elected as the DR, and the router with the second highest router ID will be elected as the BDR. Therefore, even with the highest priority on interface fa0/0, router A will not become the DR or the BDR. Router D will remain the DR and router C will remain the BDR.

In order for OSPF routers to form an adjacency, three parameters must be identical: area id, hello interval, and network type. The area id is used to group routers into OSPF areas, and routers must be in the same area to form an adjacency. The hello interval is the time interval at which OSPF routers send hello packets to discover and maintain neighbor relationships. The network type defines how OSPF operates on a particular network interface. These three parameters must match between routers to establish OSPF adjacency.

The "O*E2" in the "O*E2 0.0.0.0/0 [110/1] via 192.168.1.1, 00:05:34, Serial0/0" line represents an external OSPF route that will not increment in cost.

The number 2 indicates the number of networks advertised by OSPF.

Router A will be elected as the Designated Router (DR) for the network 10.4.0.0/16. HQ will be elected as the Backup Designated Router (BDR) for the network 10.4.0.0/16. Remote will be elected as the DR for the network 10.5.0.0/16.