19 - IPv4 Routing in the LAN

Question 1

What commands are used to configure ROAS using the physical interface for the native VLAN 1?

Answer 1

• int fa0/0
  
  • ip address 10.1.1.1 255.255.255.0
• int fa0/0.20
  
  • ip address 10.1.20.1 255.255.255.0
  • encap dot1q 20

Question 2

What commands are used to configure ROAS using a subinterface for the native VLAN 1?

Answer 2

• int fa0/0
  
  • int fa0/0.1
    
    • ip address 10.1.1.1 255.255.255.0
    • encap dot1q 1 native
  • int fa0/0.20
    
    • ip address 10.1.20.1 255.255.255.0
    • encap dot1q 20

Question 3

What ‘show’ cmds on a router can be used to verify ROAS configuration?

Answer 3

• show running-config
• show ip route
• show vlans

Question 4

In a ROAS configuration can you tell from the router whether or not the switch has been configured correctly?

Answer 4

No

Question 5

What commands are needed on a switch to prepare it to do L3 routing?

Answer 5

• sdm prefer lanbase-routing
• <then></then>
• ip routing (global cmd)

Question 6

What does the command ‘sdm prefer lanbase-routing’ do?

Answer 6

Changes switch forwarding ASIC to make room for IP Routes

Question 7

What does the global command ‘ip routing’ do?

Answer 7

• enables IPv4 routing functions
• enables commands like ‘show ip route’

Question 8

What 3 commands are used to configure an SVI?

Answer 8

• int vlan20
  
  • ip address 10.1.20.1 255.255.255.0
  • no shut

Question 9

What ‘show’ cmd allows you to verify correct configuration of an SVI?

Answer 9

‘show ip route connected’

Question 10

If an SVI doesn’t come up what 4 things should you check?

Answer 10

• the local switch has the VLAN configured
• At least one interface or trunk assigned to the VLAN must be up/up
• Make sure VLAN is ‘no shut’
• Make sure SVI is ‘no shut’

Question 11

What command changes a switch port to a router interface?

Answer 11

no switchport

Question 12

When a switchport is changed to a router interface what 4 commands will show this?

Answer 12

• show interfaces (will now show an IP address)
• show interface status (under VLAN will show ‘routed’)
• show ip route (interface now shows up as an outgoing interface in routes)
• show int gig2/1 switchport (short output)

Question 13

When configuring a L3 port channel what commands go on the physical interfaces?

Answer 13

• channel-group 1 mode on
• no switchport

Question 14

When configuring a L3 port channel what commands go on the port-channel interface?

Answer 14

• int po1
• no switchport
• ip address 10.1.1.1 255.255.255.0

Question 15

What ‘show’ cmd verifies the port-channel configuration?

Answer 15

‘show etherchannel summary’

Question 16

When troubleshooting a port-channel configuration what 3 items should you check?

Answer 16

• make sure ‘no switchport’ is configured on all interfaces
• Speed must match
• Duplex must match

Question 17

When configuring a port-channel what does the command ‘channel-group 1 mode on’ do?

Answer 17

Configures a port-channel with NO NEGOTIATION

Question 18

How do you configure an interface to participate in a PAgP-negotiated port-channel?

Answer 18

Either

1) on side A - channel-group 1 mode desirable on side B - channel-group 1 mode auto

or

2) channel-group 1 mode desirable on both sides

Question 19

How do you configure an interface to participate in a LACP-negotiated port-channel?

Answer 19

Either 1) channel-group 1 mode active or 2) channel-group 1 mode passive

Question 20

What is the difference in how a packet is handled btw an SVI and a routed interface?

Answer 20

The routed interface strips off the datalink header and adds a new one.