CCNA Final: Routing Protocols (New)

A router has two main functions. Firstly, it connects multiple IP networks by receiving packets from one network and forwarding them to another network. This allows different networks to communicate with each other. Secondly, a router determines the best path to send packets by analyzing the destination IP address and using routing protocols to find the most efficient route. By doing so, it ensures that packets reach their intended destination in the most optimal way possible.

The correct answer is that 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. This is because all router interfaces are configured with an IP address and are operational. Therefore, the router will have knowledge of the directly connected networks and include them in its routing table.

The subnet 192.168.1.64/26 should be used for the new subnet. This subnet provides enough addresses for 50 hosts while wasting a minimum of addresses. The /26 subnet mask allows for 64 addresses, which is more than enough for the 50 hosts required. Additionally, using this subnet ensures that only the necessary number of addresses are allocated, minimizing wastage.

OSPF (Open Shortest Path First) uses a hierarchical design with areas to optimize network performance and scalability. This approach reduces routing table size and limits the scope of route recalculations to specific areas, improving efficiency in large networks. OSPF's ability to segment a network into areas allows for better management of large and complex topologies, unlike RIP or EIGRP, which do not inherently support such a hierarchical structure.

The possible cause for the two routers being unable to establish an adjacency is that the hello and dead intervals are different on the two routers. The hello and dead intervals determine how often OSPF routers send hello packets to discover and maintain neighbor relationships. If the hello and dead intervals are not the same on both routers, they will not be able to synchronize their communication and establish an adjacency.

The highlighted output indicates that automatic summarization is disabled. This means that the router is not automatically summarizing the routes it learns from its neighbors when advertising them to other routers. Instead, it is advertising the specific subnets without summarizing them into larger network ranges.

If EIGRP is used with default configurations, the data will be equally distributed between two paths — A, D, B and A, C, B. This means that the data will be split between these two paths, with half of the data going through A, D, B and the other half going through A, C, B. This load balancing technique helps to optimize network performance by distributing the traffic across multiple paths, reducing congestion and improving overall efficiency.

RIP (Routing Information Protocol) uses the Bellman-Ford algorithm to determine the best path for routing within an autonomous system. This algorithm calculates the distance vector and selects the shortest path based on the number of hops. Additionally, RIP periodically sends complete routing tables to all connected devices, ensuring that all devices have the most up-to-date information about the network topology. This helps in maintaining accurate routing information and allows for efficient routing decisions.

EIGRP should be used by the network administrator to configure the router for load-balancing the traffic over unequal cost paths. EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary routing protocol that supports unequal cost load balancing. It allows the administrator to configure different metrics for different paths, enabling the router to distribute traffic across those paths based on their costs. OSPF, RIPv1, and RIPv2 do not support unequal cost load balancing, making EIGRP the correct choice for this scenario.

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 encompasses the range of IP addresses from 172.16.0.0 to 172.23.255.255, which covers all the networks on Routers 3, 4, and 5 without including any public address space or overlapping with the networks on Router1.

The reason for the problem is that one of the default routes is configured incorrectly. This means that the router is not able to properly route traffic to the operational hosts on the Internet. The incorrect configuration of the default route is causing the pings from host A to fail.

The given host address of 192.168.10.31 is actually the broadcast address for this subnet. In a network, the broadcast address is used to send data to all devices on the network. Therefore, when the PC is configured with this address as its host address, it will not be able to communicate properly with other devices on the network.

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 routing issues as the routers may not be able to properly distinguish between the two subnetworks and route traffic accordingly.

RIPv1 does not support discontiguous networks. This means that if the two networks 10.1.1.0/29 and 10.1.1.16/29 are not directly connected, RIPv1 will not be able to route traffic between them. In order for these networks to access each other, a different routing protocol that supports discontiguous networks would need to be used.

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 routes to the destination network and will distribute the traffic across these paths to achieve load balancing. This helps in optimizing network performance and ensuring efficient utilization of available resources.

EIGRP (Enhanced Interior Gateway Routing Protocol) is recommended for this network because it supports multiple protocols, including IP, IPX, and AppleTalk. EIGRP is a Cisco proprietary routing protocol that provides fast convergence, load balancing, and scalability. It is designed to work well in large and complex networks, making it a suitable choice for a network configured with multiple protocols.

Link-state routing protocols, such as OSPF and IS-IS, maintain a complete and up-to-date map of the entire network topology. This allows them to have a comprehensive understanding of the network, including all routers and links. This information is used to calculate the shortest path to each destination. Additionally, link-state protocols provide rapid convergence times in large networks as they can quickly adapt to changes in the network by flooding link-state updates and recalculating the shortest path. Therefore, the statements "They are aware of the complete network topology" and "They offer rapid convergence times in large networks" are both true.

The correct answer is "If the network uses the RIP protocol, router A will determine that all paths have equal cost." This is because RIP (Routing Information Protocol) is a distance-vector routing protocol that uses hop count as the metric to determine the best path. In RIP, all paths are considered to have equal cost if they have the same number of hops. Therefore, router A will determine that all paths to router E have equal cost and will choose one of them to forward the data.

When there is no feasible successor route to a destination network and the successor route fails, EIGRP will send queries to adjacent neighbors until a new successor route is found. This is done to determine if any of the adjacent neighbors have a feasible successor route that can be used as an alternate path to the destination network. By sending queries, EIGRP can find a new successor route and re-establish connectivity to the destination network.

The router ID in the configuration of the OSPF routing process is determined by two components: the highest IP address of any logical interface and the highest IP address of any physical interface. These two components are used to uniquely identify the router in the OSPF network. The router ID is important for the OSPF routing process as it is used to identify the router's OSPF advertisements and to establish OSPF neighbor relationships.

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 the source of the routing information, where lower values indicate higher trust. In this case, the static route has a lower administrative distance compared to the EIGRP route, so it is considered more trustworthy and is installed in the routing table.

BGP (Border Gateway Protocol) uses a path vector mechanism to maintain loop-free routing between autonomous systems (AS). It tracks the full path of routes (AS numbers) to prevent routing loops in interdomain routing. BGP ensures each AS knows the exact path a route has taken, which makes it suitable for managing routing on the Internet. This contrasts with protocols like OSPF and RIP, which operate within a single autonomous system or domain.

When the command "no ip classless" is issued on Router1, it means that Router1 will not perform classless routing and will only route packets to directly connected networks. In this case, the packet with the destination IP address of 192.168.0.26 does not fall within any directly connected network of Router1. Therefore, Router1 will not have a route to forward the packet and as a result, the packet will be dropped.

The correct answer is to configure a static route on R1 using the IP address of S0/0/0 on R2. This is because the issue is with the communication between R1 and R2, and specifically with the serial interface S0/0/0 on R2. By configuring a static route on R1 using the IP address of S0/0/0 on R2, R1 will be able to properly route traffic to R2 and resolve the problem.

The correct answer is to specify the network for which RIP routing has to be enabled. By specifying the network, the administrator can ensure that RIP routing is enabled for that specific network. This will allow the show ip protocol command to display the appropriate output.

EIGRP (Enhanced Interior Gateway Routing Protocol) is a hybrid routing protocol developed by Cisco. It combines the best features of distance-vector and link-state protocols, offering fast convergence, scalability, and efficient routing updates. Unlike purely distance-vector protocols like RIP or purely link-state protocols like OSPF, EIGRP uses a mix of both techniques to achieve efficient and reliable routing. BGP, while powerful, is mainly used as a path-vector protocol for inter-domain routing.

The reason for the packet being discarded by the Suffolk router could be that IP classless has been disabled on the router. This means that the router does not have the capability to forward packets to a network that is not directly connected to it or is not in its routing table. Since the destination address 172.29.198.5 is not directly connected to the Suffolk router and is also not in its routing table, the router discards the packet.

When network 10.0.0.0 goes down, Router5 will send a triggered update to Router4. This triggered update will inform Router4 about the failed route and will include a metric of 16 for network 10.0.0.0. This metric indicates that the route is unreachable. Therefore, the correct statement is that Router5 will send Router4 a triggered update with a metric of 16 for network 10.0.0.0.

When troubleshooting a problem with the establishment of neighbor relationships between OSPF routers, two factors that should be considered are OSPF interval timers mismatch and interface network type mismatch. If the interval timers between routers are not synchronized, it can cause issues with neighbor relationships. Additionally, if the network types configured on the interfaces of the routers do not match, it can also prevent the establishment of neighbor relationships.

The default route is configured incorrectly. This means that R1 does not have a route to forward the ping packet to the destination IP address 172.16.1.1. Since the default route is used when there is no specific route in the routing table for the destination, the ping fails because R1 does not know where to send the packet.

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From the output of the "show cdp neighbors" command, it can be determined that ABCD is a router that is connected to R1. This is because the command displays information about the neighboring devices, and in this case, it shows that ABCD is a device connected to R1. Additionally, the output also indicates that the device is connected at the Serial0/0/1 interface of R1.

The possible cause of the problem is that the routers are configured with different versions of RIP. This can cause compatibility issues and prevent devices on the 192.168.1.1 network from being able to ping devices on the 192.168.2.1 network.

The problem is caused by the configuration of router R1, which fails to include network A in the OSPF routing process. This means that router R1 is not advertising network A to other routers in the OSPF network, resulting in hosts on network B being unable to reach hosts on network A.

Routing loops can occur due to slow convergence, which is the time it takes for routers to update their routing tables after a change in the network topology. During this time, routers may still forward packets based on outdated information, leading to loops. Additionally, incorrectly configured static routes can also cause routing loops. If static routes are misconfigured, they may point to the wrong next hop or create circular paths, resulting in packets being continuously forwarded in a loop.

When a router boots, it first looks for the Cisco IOS in the flash memory. If it doesn't find the IOS there, it then tries to locate it on a TFTP server. If the IOS is not found on the TFTP server, the router will finally look for it in ROM. Therefore, the default order to locate the Cisco IOS if there is no boot system command is flash, TFTP server, ROM.

The given correct answer states that packets routed to the R2 Fast Ethernet interface require two routing table lookups. This means that when a packet is received by R2 and needs to be forwarded out of the Fast Ethernet interface, R2 will have to consult its routing table twice in order to determine the appropriate next hop for the packet. This suggests that there are multiple possible next hop options for the packet, and R2 needs to perform two lookups to determine the best one.

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 all the networks that can be reached directly from each router. This database is essential for the routers to determine the shortest path to a destination network.

CDP (Cisco Discovery Protocol) is a proprietary Cisco protocol that operates at OSI layers 1 and 2. It is enabled by default on each interface and provides information on directly connected devices that have CDP enabled. CDP can be used to test Layer 2 connectivity between devices. However, it is not used for debugging Layer 4 connectivity issues.

The OSPF LSR (Link State Request) packet is used by the receiving routers to request more information about any entry in the DBD (Database Description). This packet allows the receiving router to ask for specific information about the state of the network from the sending router. By requesting more information, the receiving router can ensure that its own database is synchronized with the sending router's database, helping to maintain accurate and up-to-date routing information within the OSPF network.

If interface Serial0/0/1 goes down on Router1, DUAL (Diffusing Update Algorithm) will query neighbors for a route to network 192.168.1.0. This means that the router will send query messages to its neighboring routers to find an alternative path to reach the network 192.168.1.0. The purpose of this is to find a feasible successor, which is a backup route that can be used in case the primary route becomes unavailable. Therefore, the correct answer is that DUAL will query neighbors for a route to network 192.168.1.0.

Before two routers can use OSPF to form a neighbor adjacency, they must agree on the network type and use the same dead interval. The network type determines how OSPF operates on a particular network segment, and both routers must agree on this to ensure proper communication. The dead interval is a timer that determines when a router is considered unreachable, and both routers must use the same dead interval for accurate neighbor detection and adjacency formation.

The first statement is true because the bootstrap program, which is a part of the router's firmware, searches for the startup configuration file in NVRAM (non-volatile random-access memory) during the boot process. This file contains the configuration settings for the router.

The fourth statement is also true because if the startup configuration file cannot be found in NVRAM, the router enters ROMMON (ROM Monitor) mode. In this mode, the router can be used to troubleshoot and recover from various issues.

Therefore, the correct answer is that the bootstrap program searches for the startup configuration file in NVRAM, and the router searches for a TFTP (Trivial File Transfer Protocol) server if the startup configuration file is absent at the default location.

The absence of R1 in the output of the show cdp neighbors command on R3 can be explained by two reasons. First, the "no cdp run" command has been run at R1, which disables the CDP protocol on R1 and prevents it from sending CDP advertisements. Second, the "no cdp enable" command has been run at the Fa0/1 interface of R3, which disables CDP on that interface and prevents R3 from receiving CDP advertisements from R1. These two actions result in R1 not being visible in the output of the show cdp neighbors command on R3.

In a network using RIP as the routing protocol, the router will use four of the five available paths to reach the destination. This is because RIP uses a maximum of four equal-cost paths to load-balance traffic. Since all paths have the same metric and the default operation is being used, the router will distribute the traffic among the four paths, providing load balancing and redundancy.

R2 does not have a route to 192.168.2.0 in its routing table. However, it has a default route (0.0.0.0/0) pointing to R1. Therefore, R2 will forward the packet to R1, which is its next hop for any unknown destination.

The exhibited output shows that the tracert command from host A to host B is unable to reach the 172.16.0.0 network and the 10.0.0.0 network. This suggests that there might be routing table issues on the network. The first possible routing table issue is that Router2 is missing a route to the 172.16.0.0 network, as indicated by the inability to reach that network. The second possible routing table issue is that Router3 is missing a route to the 10.0.0.0 network, again indicated by the inability to reach that network.

The exhibit shows the output of the "show ip route" command on Router A. The routing table does not have a route to the ISP's network, indicated by the absence of the ISP's network address in the routing table. This suggests that the link to the ISP is not being advertised by the routing protocol process running on the routers. Therefore, the correct statement is that the link to the ISP is not advertised by the routing protocol process.

R1 will forward the route information for subnet 192.168.100.0/30 because it is directly connected to R1. R1 will not forward route information for subnet 192.168.100.4/30 because it is not directly connected to R1.

The network 10.1.1.0 command has not been run on both routers. This means that the routers do not have the correct routing information for the network 10.1.1.0, which is causing them to be unable to ping the Ethernet interfaces of the other routers. Autosummarization is enabled on both routers, which means that they are summarizing the routing information for their connected networks, which could also be causing issues with routing to the specific Ethernet interfaces.