Inter-VLAN Routing

Question 1

VLANs & IP Subnets in the LAN

Answer 1

Typically a 1:1 relationship between subnets & VLANs in the LAN campus

Hosts in different subnets need to send traffic via router to communicate

Question 2

Router with Separate Interfaces

Answer 2

You need a separate physical interface for every VLAN
You’re liable to run out of interfaces

Traffic being routed within the campus has to go up & down physical ethernet cables to the router

Question 3

RoaS

Answer 3

Router on a Stick:
You configure subinterfaces instead of using separate interfaces

There’s more contention for bandwidth in this setup

Question 4

Command: Configure RoaS for F0/1

Answer 4

On Router:

interface f0/1
no ip address
no shut down

interface f0/1.10
encapsulation dot1q 10
ip address 10.10.10.1 255.255.255.0

interface f0/1.20
encapsulation dot1q 20
ip address 10.10.20.1 255.255.255.0

On Switch:
interface f0/1
switchport mode trunk

Question 5

Command: Configure Layer 3 switch for Inter-VLAN Routing

Answer 5

ip routing

interface vlan 10
ip address 10.10.10.1 255.255.255.0

interface vlan 20
ip address 10.10.20.1 255.255.255.0

Question 6

Layer 3 Switch WAN Routing Configuration

Answer 6

On the L3 switch interface connected to router:

interface f0/1
no switchport      --> Must act as a layer 3 interface
ip address 10.10.100.1 255.255.255.0
exit
ip route 0.0.0.0 0.0.0.0 10.10.100.2

On the router interface connected to the L3 switch

interface f0/1
ip address 10.10.100.2 255.255.255.0

interface f0/2 –> connected to internet/WAN
ip address 203.0.113.1 255.255.255.0
exit

ip route 0.0.0.0 0.0.0.0 203.0.113.2
ip route 10.10.0.0 255.255.0.0 10.10.100.1