CCNA Lan Chapter #6

Implementing a router-on-a-stick configuration allows the router to handle inter-VLAN traffic using a single physical interface. This is achieved by configuring subinterfaces on the router's FastEthernet interfaces, with each subinterface assigned to a specific VLAN. The router then uses a trunk link to connect to a switch, which carries traffic for all VLANs. This approach minimizes the number of physical interfaces required on the router while still allowing it to efficiently handle traffic between the VLANs.

Traditional routing uses one port per logical network, while router-on-a-stick uses subinterfaces to connect multiple logical networks to a single router port. This means that with traditional routing, each logical network requires a separate physical port on the router, which can be inefficient and lead to a lack of available ports. On the other hand, router-on-a-stick allows for multiple logical networks to be connected to a single physical port through the use of subinterfaces, which improves efficiency and reduces the need for additional physical ports.

The possible cause of the problem with the SW2 configuration is that port 0/4 is configured in access mode. In access mode, the port can only be a member of one VLAN, which means it cannot handle inter-VLAN routing. To enable inter-VLAN routing, the port should be configured in trunk mode, allowing it to carry traffic for multiple VLANs.

In a network with a limited number of VLANs, individual router physical interfaces can be used for InterVLAN routing instead of a router-on-a-stick configuration. This is because a router-on-a-stick configuration requires a single physical interface to handle traffic for multiple VLANs, which can lead to performance issues in networks with a large number of VLANs. However, in a network with a limited number of VLANs, each VLAN can be assigned to a separate physical interface on the router, allowing for better performance and efficiency in InterVLAN routing.

The likely problem is that R1 is configured for router-on-a-stick, but S1 is not configured for trunking. This means that R1 is configured to route traffic between VLANs using subinterfaces on a single physical interface, but S1 is not configured to allow the VLAN traffic to pass through the trunk link between the two devices. As a result, the devices on VLAN 2 are unable to communicate with the devices on VLAN 1.

To enable inter-VLAN routing using router-on-a-stick, the VLANs need to be created on the switch with port membership assignments. Additionally, subinterfaces on the router should be configured to match the VLANs. This allows the router to handle traffic between the VLANs by encapsulating and routing the packets based on the VLAN tags. Configuring the physical interfaces on the router and enabling a routing protocol, as well as creating VLANs on the router and defining port membership assignments on the switch, are not necessary steps for enabling inter-VLAN routing using router-on-a-stick.

The reason for the failure could be that S1 interface F0/8 is in the wrong VLAN. Since PC2 can successfully ping the F0/0 interface on R1, we can assume that the connection between R1 and S1 is functioning correctly. However, PC2 cannot ping PC1, which suggests that there may be an issue with the VLAN configuration. If S1 interface F0/8 is in the wrong VLAN, it would prevent PC2 from communicating with PC1.

The correct answer is to add a router to the topology and configure one FastEthernet interface on the router with multiple subinterfaces for VLANs 1, 10, 20, and 30. This solution allows for communication between VLANs by using a router with subinterfaces. Each subinterface is configured with a separate VLAN, allowing traffic to be routed between the VLANs. This solution minimizes the number of ports necessary to connect the VLANs as it only requires one interface on the router.

The three elements that must be used when configuring a router interface for VLAN trunking are: one subinterface per VLAN, one IP network or subnetwork for each subinterface, and a compatible trunking protocol encapsulation for each subinterface. These elements are necessary to establish communication between different VLANs over a single physical interface by creating separate logical interfaces (subinterfaces) for each VLAN, assigning IP addresses to each subinterface to enable routing between VLANs, and using a trunking protocol (such as IEEE 802.1Q or ISL) to encapsulate and carry multiple VLAN traffic over the physical interface.

The failure is caused by the incorrect network address configuration on PC3. Since PC1 can ping R1 interface F0/1, it means that the connection between PC1 and R1 is functioning correctly. However, PC1 cannot ping PC3, indicating that there is an issue with PC3's network address configuration.

The hosts connected to Fa0/1 through Fa0/5 are unable to communicate with hosts in different VLANs because the router was not configured to forward traffic for VLAN2. This means that the router is not allowing traffic to pass between VLAN2 and other VLANs.

When implementing inter-VLAN routing, it is important to configure the IP address of each subinterface as the default gateway address for each VLAN subnet. This is because the default gateway is the IP address that devices on a specific VLAN will use to route traffic to other VLANs or networks. By setting the IP address of each subinterface as the default gateway, the router will be able to properly route traffic between VLANs.

The router will forward the packet out interface FastEthernet 0/1.2 tagged for VLAN 60 because the packet's destination address matches the IP address associated with VLAN 60.

When using router-on-a-stick inter-VLAN routing, the router returns the MAC address of the physical interface in response to ARP requests. This is because the router-on-a-stick configuration involves using a single physical interface on the router to connect to multiple VLANs using subinterfaces. Each subinterface has its own VLAN and IP address, but they all share the same physical interface. When an ARP request is made, the router responds with the MAC address of the physical interface to ensure that the traffic is properly routed between the VLANs.

Subinterfaces for inter-VLAN routing require fewer router ports compared to traditional inter-VLAN routing. This is because subinterfaces allow a single physical interface on the router to be divided into multiple logical interfaces, each representing a different VLAN. Therefore, instead of requiring a separate physical interface for each VLAN, subinterfaces can handle multiple VLANs using a single physical interface. Additionally, subinterfaces also provide a less complex physical connection compared to traditional inter-VLAN routing as they eliminate the need for multiple physical connections between the router and the switch.

The first conclusion that can be drawn from the output is that both of the directly connected routes shown will share the same physical interface of the router. This can be inferred from the fact that both routes have the same next hop IP address, indicating that they are connected to the same interface.

The second conclusion is that inter-VLAN routing between hosts on the 172.17.10.0/24 and 172.17.30.0/24 networks is successful on this network. This can be determined from the presence of the "C" flag next to both routes, indicating that they are directly connected networks. Since both networks are directly connected to the router, inter-VLAN routing between them is possible.

The interface fa0/0.10 command is used in the configuration of router-on-a-stick inter-VLAN routing because it creates a subinterface. In router-on-a-stick configuration, a single physical interface is divided into multiple logical subinterfaces, each representing a different VLAN. The subinterface fa0/0.10 specifically represents VLAN 10. By configuring these subinterfaces, the router can route traffic between different VLANs using a single physical interface. Therefore, the given statements are true.

The given answer states that this network design will not scale easily, meaning that it may not be able to handle a larger number of devices or increased traffic in the future. It also mentions that the design uses more switch and router ports than necessary, indicating that there may be a more efficient way to configure the network. Lastly, it states that if the physical interfaces between the switch and router are operational, the devices on different VLANs can communicate through the router, suggesting that the router plays a crucial role in facilitating communication between VLANs.

The failure to ping PC2 could be due to the incorrect encapsulation command on the R1 F0/0.3 interface. This means that the encapsulation settings on the interface do not match the requirements of the network, preventing successful communication between PC1 and PC2.

The first statement is true because subinterface fa0/0.2 is specifically configured to process incoming traffic with a VLAN ID of 2. The second statement is also true because the traffic inbound on this router is indeed processed by different subinterfaces, depending on the VLAN from which the traffic originated.