A Quiz On CCNA WAN Chapter 3

In a Frame Relay network, a virtual circuit is created between two DTEs. A virtual circuit is a logical connection established over a physical network that allows data to be transmitted between the two devices. It provides a reliable and efficient means of communication, as it can dynamically allocate bandwidth based on the data traffic. This allows for optimal utilization of network resources and ensures that data is transmitted in a timely manner. Therefore, in a Frame Relay network, a virtual circuit is created between two DTEs to facilitate communication.

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The correct answer is two point-to-point subinterfaces. This is because the traffic between R1 and R2 needs to travel through HQ first, which means that there needs to be a direct connection between each router and HQ. Using two point-to-point subinterfaces allows for a dedicated connection between each router and HQ, ensuring that the traffic flows properly.

The correct answer is the fourth option. This is because it configures R2 and R3 with point-to-point frame relay connections using DLCIs 201 and 301 respectively. This configuration allows each router to have direct connectivity to R1 without any intermediate routers.

Based on the given output, the Frame Relay switch is experiencing congestion. This can be determined because the output shows that the number of frames discarded due to congestion is increasing. This indicates that the switch is unable to handle the incoming traffic and is dropping frames to alleviate the congestion.

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Point-to-point subinterfaces act like leased lines and eliminate split-horizon routing issues. This means that with point-to-point subinterfaces, there is a direct connection between two devices, allowing for efficient and direct communication without the need for split-horizon routing, which can cause routing loops. This makes point-to-point subinterfaces a reliable and effective choice for connecting devices in a network.

Inverse ARP and LMI status messages are the two items that allow the router to map data link layer addresses to network layer addresses in a Frame Relay network. Inverse ARP is used to dynamically map network layer addresses to data link layer addresses, allowing the router to determine the appropriate DLCI (Data Link Connection Identifier) for communication. LMI (Local Management Interface) status messages are used by the router to exchange information with the Frame Relay switch, including mapping tables that associate DLCIs with network layer addresses.

The likely cause for R2 not exchanging OSPF information correctly is that the frame-relay map command is missing the broadcast keyword. This keyword is necessary in order for OSPF updates to be sent as broadcast frames over the Frame Relay network. Without the broadcast keyword, OSPF updates will be sent as unicast frames, which will not be properly propagated to all routers in the network.

A data-link connection identifier (DLCI) is a locally significant address used to identify a virtual circuit. In a Frame Relay network, virtual circuits are used to establish connections between devices. Each virtual circuit is assigned a unique DLCI which serves as an identifier for that specific circuit. The DLCI allows devices to differentiate between different virtual circuits and route data accordingly. Therefore, the DLCI is a locally significant address that is used to identify a virtual circuit within a Frame Relay network.

The point-to-point configuration on subinterface S0/0.110 eliminates split horizon issues without increasing the likelihood of routing loops. Split horizon is a technique used in distance-vector routing protocols to prevent routing loops by not advertising a route back out of the interface it was learned from. In a point-to-point configuration, there is only one other interface connected, so there is no need for split horizon. Additionally, the point-to-point configuration does not increase the likelihood of routing loops because there is only one possible path between the two interfaces.

Using Frame Relay allows customers to only pay for the local loop and the bandwidth they need to purchase from the network provider. This is a benefit compared to using a leased line or ISDN service, where customers would have to pay for an end-to-end connection that includes the local loop and the network link. With Frame Relay, customers have more flexibility in defining their virtual circuit needs and can choose smaller increments of bandwidth as low as 64 kbps. It also allows for lower cost circuit installations when connecting new sites, compared to the costs of ISDN dialup or adding additional hardware for leased service.

The output indicates that the command "encapsulation frame-relay ietf" has been used on the Serial 0/0/0 interface of router R1.

When a Frame Relay switch detects an excessive build-up of frames in its queue, it performs three actions. Firstly, it drops frames from the queue that have the DE (Discard Eligible) bit set. This helps to free up space in the queue for incoming frames. Secondly, it sets the FECN (Forward Explicit Congestion Notification) bit on all frames it receives on the congested link. This notifies the connected devices that the link is congested and they should slow down transmission. Lastly, it sets the BECN (Backward Explicit Congestion Notification) bit on all frames it places on the congested link. This informs the connected devices that the switch itself is congested and they should slow down transmission.

When using RIP on Frame Relay multiaccess networks, address-to-DLCI mapping must be done using the frame-relay map command with the broadcast keyword. This is necessary to forward routing updates. By using this command, the router will map IP addresses to specific DLCIs and send the updates as broadcast traffic. This ensures that the updates reach all the other routers on the Frame Relay network. Without this mapping, the updates would not be properly forwarded and the routing information would not be propagated correctly.

The output shows that Serial 0/0/0 has been configured with an DLCI of 201.

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The correct answer is R2(config-if)# frame-relay map ip 10.1.1.3 201 broadcast and R3(config-if)# frame-relay map ip 10.1.1.2 301 broadcast. This is because the frame-relay map command is used to map an IP address to a specific DLCI on a Frame Relay interface. In order for all routers to ping each other successfully, R2 needs to map the IP address 10.1.1.3 to DLCI 201, and R3 needs to map the IP address 10.1.1.2 to DLCI 301. By using the broadcast keyword, the routers will be able to send broadcast traffic across the Frame Relay network.

Frame Relay technology does not have its own error recovery mechanism. Instead, it relies on upper layer protocols to handle error recovery. This means that Frame Relay services depend on protocols like TCP or UDP to detect and recover from errors in the transmitted frames. Additionally, when a receiving device detects an error in a frame, it simply drops the frame without notifying the sender. This means that the sender is not aware that errors occurred and does not need to retransmit the frame.

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The first probable reason for the problem is that the router is not configured for the same Frame Relay PVC as the switch. This means that the router and the switch are not using the same virtual circuit for communication, causing a mismatch.

The second probable reason is that the LMI type on the Frame Relay switch is not ANSI. LMI (Local Management Interface) is used for communication between the router and the Frame Relay switch. If the LMI type is not set to ANSI, it can cause compatibility issues and prevent proper communication between the devices.