Ch.17 Routing in the LAN

Question 1

What are the four ways to configure VLAN routing

Answer 1

1. Use a router, with one router LAN interface and cable connected to the switch for each and every VLAN
2. Use a router, with a VLAN trunk connecting to a LAN switch (Known as router on a stick ROAS)
3. Use a layer 3 switch with switched virtual interfaces (SVI)
4. Use a Layer 3 switch with routed interfaces (which may or may not be Layer 3 EtherChannels)

Question 2

Describe Router on a stick (ROAS)

Answer 2

When a router uses VLAN trunking configuration to give the router a logical router interface connected to each VLAN

Question 3

What is a subinterface

Answer 3

One of the virtual interfaces on a single physical interface (ex. interface G0/0.20) - The .20 is a VLAN

Question 4

What is the first step in configuring 802.1Q trunking on a router

Answer 4

Use the interface type number.subint command in global config mode to create a unique sub interface for each VLAN that needs to be routed

Question 5

What is the second step in configuring 802.1Q trunking on a router

Answer 5

Use the encapsulation dot1q valn_id command in subinterface mode to enable 802.1q and associate one specific VLAN with the subinterface

Question 6

What is the third step in configuring 802.1Q trunking on a router

Answer 6

Use the ip address address mask command in subinterface configuration mode to configure IP settings (address and mask)

Question 7

what does the encapsulation command do when configuring a VLAN

Answer 7

enables trunking and defines the VLAN whose frames are considered to be coming in and out of the interface

Question 8

What are the two steps to define a router interface for the antive VLAN

Answer 8

1. COnfigure the ip address command on the physical interface, but without an encapsulation command, the router considers this physical interface to be using the native VLAN
2. Configure the ip address command on a subinterface and use the encapsulation dot1q vlan-id native subcommand to tell the router both the VLAN ID and the fact that it is the native VLAN

Question 9

What is the first step in Troubleshooting ROAS (Router on a stick)

Answer 9

Is each non-native VLAN configured on the router with an encapsulation dot1q vlan-id command on a subinterface?

Question 10

What is the second step in Troubleshooting ROAS (Router on a stick)

Answer 10

DO the same VLANs exist on the trunk on the neighboring switch (show interfaces trunk), and are they in the allowed list, not VTP pruned, and not STP blocked

Question 11

What is the third step in Troubleshooting ROAS (Router on a stick)

Answer 11

Does each router ROAS subinterface have an IP address/mask configured per the planned configuration

Question 12

What is the fourth step in Troubleshooting ROAS (Router on a stick)

Answer 12

If using the native VLAN, is it configured correctly on the router either on a subinterface (with an encapsulation dot1q vlan-id native command) or implied on the physical interface

Question 13

What is the fifth step in Troubleshooting ROAS (Router on a stick)

Answer 13

Is the same native VLAN configured on the neighboring switchs trunk in comparison to the native VLAN configured on the router

Question 14

What is the sixth step in Troubleshooting ROAS (Router on a stick)

Answer 14

Are the router physical or ROAS subinterfaces configured with a shutdown command

Question 15

What is the first step to enable IP routing on the switch

Answer 15

Use the sdm prefer lanbase-routing command in global config mode to change the switch forwarding ASIC settings to make space for IPc4 routes at the next reload of the switch

Question 16

What is the second step to enable IP routing on the switch

Answer 16

Use the reload EXEC command in enable mode to reload (reboot) the switch to pick up the new sdm prefer command setting

Question 17

What is the third step to enable IP routing on the switch

Answer 17

Once reloaded, use the ip routing command in global configuration mode to enable the IPv4 routing function in IOS software and to enable key commands like show Ip route

Question 18

What is the first step of Configuring each SVI interface, one per VLAN for which routing should be done by this Layer 3 switch

Answer 18

Use the interface vlan vlan_id command in gloabl configuration mode to create a VLAN interface and to give the switchs routing logic a layer 3 interface connected into the VLAN of the same number

Question 19

What is the second step of Configuring each SVI interface, one per VLAN for which routing should be done by this Layer 3 switch

Answer 19

Use the ip address address mask command in VLAN interface configuration mode to configure an IP address and mask on the VLAN interface, enabling IPv4 routing on that VLAN interfce

Question 20

What is the third step of Configuring each SVI interface, one per VLAN for which routing should be done by this Layer 3 switch

Answer 20

Use the no shutdown command in interface config mode to enable the VLAN interface

Question 21

What is a routed port

Answer 21

A port on a multilayer cisco switch, configured with the no switchport command, that tells the switch to treat the port as if it were a layer 3 port, like a router interface