CCNA Routing Protocols & Concepts Final

The TTL (Time to Live) field in an IP packet header is used to limit the period of time or number of hops a packet can traverse through the network before it should be discarded. This prevents packets from circulating indefinitely in the network and ensures that they do not consume excessive network resources. The TTL value is decremented by each router the packet passes through, and when it reaches zero, the packet is discarded. Therefore, the TTL field helps in efficient network routing and prevents packets from lingering in the network indefinitely.

Routers compare metrics to determine the best route. Routing protocols use different metrics to evaluate the quality of a route, such as bandwidth, delay, reliability, and load. These metrics are assigned values, and routers compare these values to determine which route is the most favorable. The router selects the route with the lowest metric, as it represents the best path. Therefore, the statement that routers compare metrics to determine the best route is true.

If no routing protocols or static routes are configured, the only routes that will be included in the show ip route command output for router A are the directly connected networks. In this case, the router interfaces are configured with IP addresses in the 192.168.x.0 range, so the routes to networks 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 will be in the routing table.

When the show cdp neighbors command is issued from Router C, the output will display devices B and D. The command shows the directly connected devices using the Cisco Discovery Protocol (CDP), and in this case, Router C is directly connected to devices B and D.

The answer is S 192.168.168.0/24 [1/0] via 192.168.200.1. This is because the route with the lowest administrative distance (AD) is always preferred. In this case, the static route (S) has an AD of 1, which is lower than the AD of the other routes. Therefore, the router will use the static route to reach network 192.168.168.0.

The exhibit suggests that the missing information for Blank 1 is the command "show ip route" because the output shown is related to routing information. The missing information for Blank 2 is the number 120 because the output shows a metric value of 120 for the specific route. The missing information for Blank 3 is the letter C because the output indicates that the route is directly connected, which is denoted by the letter C in routing tables.

RIP (Routing Information Protocol) uses triggered updates to announce network changes if they happen in between the periodic updates. This means that instead of waiting for the next scheduled update, RIP immediately sends an update when a network change occurs. By doing so, RIP reduces the convergence time in a larger network, ensuring that all routers have the most up-to-date routing information in a timely manner. This helps to maintain efficient and accurate routing throughout the network.

The highlighted value 192 in the routing table represents the metric, which is the cost. The metric is a value used to determine the desirability of a particular route. In this case, the higher the metric, the higher the cost associated with using that route. The Dijkstra algorithm assigns this metric to designate the number of hops in the network, indicating the number of routers that need to be traversed to reach the destination.

Link-state routing protocols are aware of the complete network topology, meaning that they have knowledge of all the routers and links in the network. This allows them to make more informed routing decisions based on the current state of the network. Additionally, link-state routing protocols offer rapid convergence times in large networks. Convergence refers to the time it takes for all routers in the network to have consistent routing information after a change in the network topology. Link-state protocols use algorithms that quickly calculate the shortest path to each destination, resulting in faster convergence times compared to other routing protocols.

When adding a network to the OSPF routing process configuration, three things are required. Firstly, the network address needs to be specified to identify the network being added. Secondly, an area ID is needed to determine the OSPF area to which the network belongs. Lastly, a wildcard mask is required to define the range of IP addresses within the network. The loopback address and autonomous system number are not necessary for adding a network to the OSPF routing process configuration.

The correct answer is "R1(config-router)# network 172.16.0.0 0.0.31.255 area 0". This command is used to advertise the entire range of addresses included in the 172.16.0.0/19 network in area 0. The subnet mask 0.0.31.255 indicates that all bits in the third octet and the first 5 bits in the fourth octet will be included in the network advertisement. This will cover all the addresses from 172.16.0.0 to 172.16.31.255.

A router performs packet switching, which involves receiving data packets from one network and forwarding them to the appropriate network based on their destination IP addresses. This allows for efficient and reliable transmission of data between different networks. Additionally, routers are responsible for path selection, which involves determining the best path for data packets to travel through a network based on factors such as network congestion, speed, and reliability. By choosing the most optimal path, routers ensure that data packets reach their destination in a timely manner.

After the IOS loads from flash, the next step in the router boot sequence is to locate and load the startup-config file from NVRAM. This file contains the configuration settings that were previously saved and allows the router to boot up with the correct configuration.

The correct answer is "S 172.16.1.0 [1/0] via 172.16.2.2". The "S" in the answer stands for "static", indicating that the route was manually configured by the network administrator. The IP address 172.16.1.0 is reachable via the next hop IP address 172.16.2.2. The [1/0] indicates the administrative distance and metric of the route.

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The network administrator should use show and debug commands to determine if hellos are propagating. This step will help in troubleshooting the problem because OSPF uses hello packets to establish and maintain neighbor relationships between routers. If the hellos are not propagating, it indicates a potential issue with the OSPF configuration or connectivity between routers. By analyzing the output of show and debug commands related to OSPF, the administrator can identify any errors or inconsistencies that may be causing BOS to not have the 10.0.0.0/24 network in its routing table.

Router2 can advertise the summary address 172.16.0.0/13 to Router1 in order to reach the three networks on Routers 3, 4, and 5 without advertising any public address space or overlapping the networks on Router1. This summary address covers the range from 172.16.0.0 to 172.23.255.255, which includes all the networks on Routers 3, 4, and 5.

The command "B(config)# router rip B(config-router)# passive-interface S0/0" will prevent RIP updates from being sent to Router A. By configuring the interface S0/0 as passive, the router will not send RIP updates out through that interface. This means that Router A, which is connected to interface S0/0, will not receive any RIP updates.

The cause of the PC not communicating properly with the network is that the address 192.168.10.31 is the broadcast address for this subnet. Broadcast addresses are used to send data to all devices on a network, so assigning it as a host address would prevent proper communication with other devices.

The correct answer is "It will load balance the traffic between ADC and ABC". This means that traffic from the 172.16.1.0/24 network will be evenly distributed between the ADC and ABC paths to reach the 10.0.0.0/24 network.

The correct answer is Paris(config)# router eigrp 100, Paris(config-router)# network 192.168.7.0, Paris(config-router)# network 192.168.8.0. These three commands are needed to configure EIGRP on the Paris router. The first command "Paris(config)# router eigrp 100" enables EIGRP routing process on the router with autonomous system number 100. The next two commands "Paris(config-router)# network 192.168.7.0" and "Paris(config-router)# network 192.168.8.0" specify the network addresses that will participate in EIGRP routing.

The correct answer is that the router installs all the equal cost paths in the routing table and performs equal cost load balancing to send packets out multiple exit interfaces. This means that the router will have multiple paths to choose from when sending packets from the 172.16.1.0/16 network to the 192.168.200.0/24 network. It will distribute the traffic evenly across these paths to prevent congestion and ensure efficient utilization of the network.

The correct route for a packet with a destination address of 10.1.4.1 would be 0.0.0.0/0 via 192.168.0.1. This is because the destination address falls outside of the specific routes mentioned (10.1.0.0/22, 10.1.0.0/23, and 10.1.0.0/24). The 0.0.0.0/0 route is the default route, which means it will be used when there is no specific route available for the destination. The next hop for this default route is 192.168.0.1.

The correct answer is "Router_A(config-router)# default-information originate". This command will save the administrator the time and trouble of configuring the default route on Router_B and all of the other routers in the OSPF area because it will advertise the default route to all other routers in the OSPF area. By using this command, Router_A will inject the default route into the OSPF routing domain, allowing all routers in the OSPF area to learn about and use the default route.

When the command "no ip classless" is issued on Router1, it means that Router1 is no longer allowed to forward packets to a network that is not directly connected. In this case, the packet with the destination IP address 192.168.0.26 is not directly connected to Router1, so it will be dropped instead of being forwarded.

Changing the IP address on Serial 0/1/0 on router 2 to 192.168.0.1/30 will correct the problem because the IP addresses on both routers must be in the same subnet in order for them to communicate with each other. By changing the IP address on router 2 to 192.168.0.1/30, it will be in the same subnet as the IP address on router 1, allowing them to establish a connection and resolve the ping failure.

The hosts on the 10.0.0.0/24 network would not be able to ping hosts on the Fa0/0 LAN of the JAX router because the JAX router does not have the network 192.168.3.0 0.0.0.255 area 0 command configured. This command is necessary for the JAX router to advertise the 192.168.3.0 network to other routers in the network, allowing for proper routing and connectivity between the 10.0.0.0/24 network and the Fa0/0 LAN of the JAX router.

When network 10.0.0.0 goes down, Router5 will immediately send a triggered update to Router4 with a metric of 16 for the network 10.0.0.0. This is because RIP uses a hop count metric, and a metric of 16 represents an unreachable network. The triggered update is sent immediately to inform Router4 about the failure, rather than waiting for the next periodic update.

When a packet travels through a router, it modifies the TTL (Time to Live) field by decrementing it by one. This is done to ensure that the packet does not circulate indefinitely in the network. The router also maintains the same source and destination IP addresses, meaning that these addresses do not change during the routing process. However, the router does change the source physical address to the physical address of the exit interface. This is necessary because the packet is now being sent out through a different interface, so the physical address needs to be updated accordingly.

The correct answer is that the route via Path A is installed because the static route has the lowest administrative distance to network 10.2.0.0/16. Administrative distance is a measure of the trustworthiness of a routing protocol. A lower administrative distance indicates a higher trust level, and in this case, the static route has a lower administrative distance than the EIGRP route. Therefore, R1 will install the route via Path A in its routing table.

The exhibited commands do not specify any encryption method for passwords. By default, Cisco routers encrypt only the enable password using the type 7 encryption algorithm. Therefore, the correct answer is that only the enable password is encrypted.

The problem with the addressing used in the topology is that the subnetwork configured on the serial link between Router1 and Router2 overlaps with the subnetwork assigned to Ethernet0 of Router3. This can cause conflicts and confusion in routing traffic, as the routers may not be able to determine the correct path for the data packets.

The devices labeled "?" in the graphic could be DCE (Data Circuit-terminating Equipment), CSU/DSU (Channel Service Unit/Data Service Unit), and modem. DCE refers to the equipment that connects the data terminal equipment (DTE) to a communication network. CSU/DSU is a device that connects a digital circuit to a communication network. A modem is a device that modulates and demodulates signals to transmit data over communication lines. These devices are commonly used in networking to establish connections and facilitate data transmission.

The correct answer is EIGRP traffic will use the path Router1, Router3, Router4, Router5 because it has the best metric. This means that EIGRP will calculate the metric for each path and choose the one with the lowest metric value, which indicates the best path. In this case, the path through Router1, Router3, Router4, Router5 has a lower metric than the path through Router1, Router2, Router5. Therefore, EIGRP will route traffic between the Router1 LAN and Router5 LAN through the path with the best metric.

The most efficient summarization of the routes attached to router R1 is 198.18.48.0/21. This summarization includes all the given routes and provides the most concise representation of the network addresses.

Split horizon is a mechanism used in distance-vector routing protocols, such as RIPv2, to prevent the routing loops. In this scenario, if network 10.0.0.0 goes down, split horizon will prevent Router1 from advertising false routing information back to Router2. Split horizon states that a router should not advertise a route back to the same interface from which it learned the route. This helps to avoid loops in the network by preventing a router from advertising a route back to the router it learned it from.

The router will need to perform a recursive lookup for packets destined to the 10.0.0.0/8 network and the 192.168.2.0/24 network. This is because these networks are not directly connected to the router and are not in the router's routing table. Therefore, the router will need to consult its routing table and potentially query other routers to determine the next hop for these packets.

The OSPF LSU packet is used to announce new OSPF information and to reply to certain types of requests. This means that when a router has new OSPF information, such as changes in its routing table, it will use the LSU packet to inform other OSPF routers in the network about these changes. Additionally, the LSU packet can also be used to respond to specific requests made by other routers in the network.

When a router is presented with multiple valid routes to a destination, it first considers the routes with the lowest administrative distance. Administrative distance is a value assigned to each routing protocol, indicating its trustworthiness or priority. The routes with the lowest administrative distance are then further evaluated based on their metric. The metric is a value that represents the desirability or efficiency of a route. The routes with the best metric, meaning the most optimal or efficient, are finally added to the routing table. This process ensures that the router selects the most reliable and efficient routes for forwarding network traffic.

Before two routers can form a neighbor adjacency using OSPF, they must first agree on the network type. This is important because OSPF supports different network types, such as broadcast, point-to-point, and non-broadcast multi-access. The routers need to agree on the network type to ensure proper communication and neighbor formation. Additionally, the routers must use the same dead interval. The dead interval is the time that a router waits before declaring a neighboring router as dead. If the routers have different dead intervals, it can lead to inconsistencies and instability in the OSPF network.

CDP (Cisco Discovery Protocol) is a Cisco proprietary protocol used to gather information about directly connected Cisco devices. It allows network administrators to verify Layer 2 connectivity between devices, making it easier to troubleshoot and diagnose network issues. CDP is enabled by default on each interface of Cisco devices, providing automatic discovery and information gathering capabilities. It does not provide a layer of security and is not used for debugging Layer 4 connectivity issues. Therefore, the three correct features of CDP are: testing Layer 2 connectivity, being enabled by default on each interface, and providing information on directly connected devices that have CDP enabled.

Based on the exhibit, there are two routes that are both level 1 and qualify for use as an ultimate route. The other routes either do not meet the level 1 requirement or do not qualify as an ultimate route. Therefore, the correct answer is 2.

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The three true statements about the routing table for Router1 are: the AD of EIGRP routes has been manually changed to a value other than the default value, Router1 is running both the EIGRP and OSPF routing process, and no default route has been configured.

When troubleshooting a problem with the establishment of neighbor relationships between OSPF routers, three factors that should be considered are OSPF interval timers mismatch, interface network type mismatch, and inconsistent authentication configuration.

OSPF interval timers mismatch refers to a situation where the routers have different settings for the Hello and Dead intervals, causing communication issues. Interface network type mismatch occurs when the routers have different network types configured on their interfaces, preventing them from forming a neighbor relationship. Inconsistent authentication configuration refers to a situation where the routers have different authentication settings, such as different passwords or encryption algorithms, which can also prevent neighbor relationships from forming.

The reason for the packet being discarded by the Suffolk router is that the "ip classless" command is not enabled on the router. This command allows the router to forward packets to a default route even if it does not have a specific route for the destination network. Without this command, the Suffolk router will only forward packets to destinations for which it has a specific route, and since there is no specific route for the destination address 172.29.198.5, the packet is discarded.

The first step OSPF and IS-IS routers take in building a shortest path first database is to learn about directly connected networks. This means that the routers gather information about the networks that are directly connected to them, such as their IP addresses and subnet masks. This information is then used to create a database of the network topology, which helps the routers determine the shortest path to a destination network.

If interface s0/0/1 goes down on Router1, DUAL (Diffusing Update Algorithm) will query its neighbors for an alternative route to the network 192.168.1.0. This is because DUAL is the algorithm used by Cisco routers to calculate the best path to a network. When a link fails, DUAL will search for a feasible successor, which is a backup route that meets certain criteria. In this case, DUAL will query the neighbors to find an alternative route to the network 192.168.1.0.

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The OSPF routing protocol elects designated routers on multiaccess links, which helps in efficient routing in large networks. EIGRP supports unequal cost load balancing, allowing for better utilization of network resources. RIP does not advertise a route beyond a hop count of 15, which helps prevent routing loops and ensures efficient routing in smaller networks.