Module 4 - Inter-VLAN Routing

Question 1

A PC is to access a web server on another network. Which inter-VLAN method will provide the highest bandwidth at Layer 3 and also provide a default gateway for the PC?

Multilayer switch with routing enabled

Trunked interface between the router and the switch

Router on a stick

Multiple physical interfaces on the router, all connected to a Layer 2 switch

Answer 1

Multilayer switch with routing enabled

Topic 4.3.0 - A router-on-a-stick design is the same as having a trunked interface between the router and the switch. This design works, but does not scale well because all VLANs must traverse the one connection between the router and the switch. Multiple physical interfaces on the router would be faster than the router-on-a-stick design, but a router has a limited number of physical interfaces. Layer 3 switches with routing enabled have more Ethernet ports as well as the ability to route.

Question 2

Which scalable method must be implemented in order to provide inter-VLAN routing on a switched network with more than 1000 VLANs?

Configuring static routes on a Layer 2 switch device

Connecting a router interface to a switch port that is configured in trunk mode to route packets between VLANs, with each VLAN assigned to a router subinterface

Connecting each physical router interface to a different physical switch port, with each switch port assigned to a different VLAN

Routing traffic internally to a Layer 3 switch device

Answer 2

Routing traffic internally to a Layer 3 switch device

Topic 4.1.0 - Layer 2 switches are able to perform static routing, but this method is inefficient with a large number of VLANs. Multilayer switching is more scalable than any other inter-VLAN routing implementation, with traffic being routed internally to the switch device. In router-on-a-stick inter-VLAN routing, where a single physical interface routes traffic among multiple VLANs on a network, there is no practical scalability. The legacy inter-VLAN routing is very inefficient and is no longer used in switched networks, because each VLAN requires a physical router interface that is connected to a different physical switch port.

Question 3

When configuring a router as part of a router-on-a-stick inter-VLAN routing topology, where should the IP address be assigned?

To the subinterface
To the interface
To the VLAN
To the SVI

Answer 3

To the subinterface

Topic 4.2.0 - The IP address and the encapsulation type should be assigned to each router subinterface in a router-on-a-stick inter-VLAN topology.

Question 4

A small college uses VLAN 10 for the classroom network and VLAN 20 for the office network. What is needed to enable communication between these two VLANs while using legacy inter-
VLAN routing?

A router with one VLAN interface is needed to connect to the SVI on a switch.

A router with at least two LAN interfaces should be used.

A switch with a port that is configured as trunk is needed to connect to a router.

Two groups of switches are needed, each with ports that are configured for one VLAN.

Answer 4

A router with at least two LAN interfaces should be used.

Topic 4.1.0 - With legacy inter-VLAN routing, different physical router interfaces are connected to different physical switch ports. The switch ports that connect to the router are in access mode, each belonging to a different VLAN. Switches can have ports that are assigned to different VLANs, but communication between VLANs requires routing function from the router.

Question 5

What is a disadvantage of using multilayer switches for inter-VLAN routing?

Multilayer switches are more expensive than router-on-a-stick implementations.

Multilayer switches are limited to using trunk links for Layer 3 routing.

Spanning tree must be disabled in order to implement routing on a multilayer switch.

Multilayer switches have higher latency for Layer 3 routing.

Answer 5

Multilayer switches are more expensive than router-on-a-stick implementations.

Topic 4.1.0 - The main disadvantage of the multilayer switches is their higher cost.
Because both routing and switching are done in hardware, multilayer switches are faster than router-on-a-stick.

Question 6

Which type of inter-VLAN communication design requires the configuration of multiple subinterfaces?

Legacy inter-VLAN routing

Router on a stick

Routing via a multilayer switch

Routing for the management VLAN

Answer 6

Router on a stick

Topic 4.1.0 - The router-on-a-stick design always includes subinterfaces on a router.
When a multilayer switch is used, multiple SVIs are created. When the number of VLANs equals the number of ports on a router, or when the management VLAN needs to be routed, any of the inter-VLAN design methods can be used.

Question 7

What is a disadvantage of using router-on-a-stick inter-VLAN routing?

Does not scale well beyond 50 VLANS

Requires the use of multiple router interfaces configured to operate as access links

Does not support VLAN-tagged packets

Requires the use of more physical interfaces than legacy inter-VLAN
routing

Answer 7

Does not scale well beyond 50 VLANS

Topic 4.1.0 - Router-on-a-stick inter-VLAN routing does not scale beyond 50 VLANs. The router can receive VLAN-tagged packets and send VLAN-tagged packets to a destination. Router-on-a-stick inter-VLAN routing can utilize a single router interface as a trunk link to receive and forward VLAN traffic and does not require multiple interfaces.

Question 8

What is the meaning of the number 10 in the encapsulation dot1Q 10 native router subinterface command?

The VLAN ID
The subinterface number
The interface number
The subnet number

Answer 8

The VLAN ID

Topic 4.2.0 - The administrator can use the encapsulation command to specify the encapsulation type (IEEE 802.1Q or ISL), the VLAN ID, and optionally the native VLAN.

Question 9

While configuring inter-VLAN routing on a multilayer switch, a network administrator issues the no switchport command on an interface that is connected to another switch. What is the purpose of this command?

To provide an access link that tags VLAN traffic

To create a routed port for a single network

To create a switched virtual interface

To provide a static trunk link

Answer 9

To create a routed port for a single network

Topic 4.3.0 - When a Layer 2 interface on a multilayer switch is configured with the no switchport command, it becomes a routed port. A routed port is configured with an IP address for a specific subnet.

Question 10

A network administrator enters the following command sequence on a Cisco 3560 switch.
What is the purpose of these commands?

Switch(config)# interface gigabitethernet 0/1
Switch(config-if)# no switchport

To enable the GiO/1 port as a bridge virtual interface

To make the Gio/1 port a routed port

To shut down the GiO/1 port

To enable the GiO/1 port as a switch virtual interface

Answer 10

To make the Gio/1 port a routed port

Topic 4.3.0 - By default, the physical ports on a 3560 switch are Layer 2 interfaces. To make them routed ports, the interface command no switchport should be used. The other options do not describe the purpose of this command.

Question 11

What operational mode should be used on a switch port to connect it to a router for router-on-a-stick inter-VLAN routing?

Trunk
Access
Dynamic desirable
Dynamic auto

Answer 11

Trunk

Topic 4.2.0 - Routers do not support Dynamic Trunking Protocol, and access mode is used to connect hosts.

Question 12

Which sentence correctly describes the SVI inter-VLAN routing method?

Subinterfaces have to be created.

The encapsulation type must be configured on the SVI.

An SVI is needed for each VLAN.

A physical interface is needed for every VLAN that is created.

Answer 12

An SVI is needed for each VLAN.

Topic 4.1.0 - In order to create SVI inter-VLAN routing on a Layer 3 switch, the VLAN must exist in the database and the SVI must be explicitly created. The only exception is VLAN1, which is created by default.

Question 13

How is traffic routed between multiple VLANs on a multilayer switch?

Traffic is routed via internal VLAN interfaces.

Traffic is broadcast out all physical interfaces.

Traffic is routed via physical interfaces.

Traffic is routed via subinterfaces.

Answer 13

Traffic is routed via internal VLAN interfaces.

Topic 4.1.0 - Multilayer switches can perform inter-VLAN routing by the use of internal
VLAN interfaces. External physical interfaces can receive traffic but are not necessary for routing functions. When routing between VLANs, any broadcast traffic that is received on a VLAN would remain on ports that are members of that VLAN. Subinterfaces are not usable for inter-VLAN routing on multilayer switches.

Question 14

What is required to perform router-on-a-stick inter-VLAN routing?

A router with multiple physical interfaces

A multilayer switch

A Layer 2 switch that is configured with multiple trunk ports

A router that is configured with multiple subinterfaces

Answer 14

A router that is configured with multiple subinterfaces

Topic 4.2.0 - With router-on-a-stick inter-VLAN routing, a single physical router interface is used to route packets between multiple VLANs if the interface is configured with multiple subinterfaces. A separate subinterface is needed for each VLAN that will be routed. Because the router is performing all routing functions, a multilayer switch is not required.

Question 15

An administrator was troubleshooting a router-on-a-stick topology and concluded that the problem was related to the configuration of VLANs on the router subinterfaces. Which two commands can the administrator use in the router to identify the problem? (Choose two.)

show controllers
show ip protocols
show vlan
show ip interface
show running-config

Answer 15

show ip interface
show running-config

Topic 4.4.0 - The show ip interface and show running-config commands can be useful in troubleshooting routing issues like wrong VLAN IDs that are assigned to subinterfaces. The show controllers and show ip protocols commands do not display any information about VLANs. The show vlan command is not useful to show information about the router subinterfaces.