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Lab 01Hands-on Lab

Implement Inter-VLAN Routing

Routing & VLANs

Goal

Route between VLANs using router-on-a-stick (subinterfaces) on R1, with switches S1/S2 trunked and PCs in VLAN 10, 20, 30.

VLAN802.1QTrunkSubinterfacesRouting
1

Implement Inter-VLAN Routing

Route between VLANs using router-on-a-stick (subinterfaces) on R1, with switches S1/S2 trunked and PCs in VLAN 10, 20, 30.

R1#
enable
configure terminal
hostname R1
no ip domain-lookup
enable secret class
line console 0
 password cisco
 login
exit
line vty 0 4
 password cisco
 login
exit
banner motd # Authorized access only #

Routing & VLANs

2

Basic Device Settings

Apply the same baseline settings on R1, S1 and S2 before building the network.

R1#
vlan 10
 name VLAN10
vlan 20
 name VLAN20
vlan 30
 name VLAN30
!
interface fastEthernet 0/6     ! PC-A
 switchport mode access
 switchport access vlan 10
interface fastEthernet 0/11    ! PC-B
 switchport mode access
 switchport access vlan 20
interface fastEthernet 0/18    ! PC-C
 switchport mode access
 switchport access vlan 30
3

IMPORTANT: Use the exact addressing table in YOUR lab window. The addresses below are the standard SRWE values, shown as a template only.

Create VLANs

R1#
! on S1 — trunk toward R1
interface g0/1
 switchport mode trunk
 switchport trunk allowed vlan 10,20,30
!
! on S1 and S2 — switch-to-switch trunk
interface g0/2
 switchport mode trunk
 switchport trunk allowed vlan 10,20,30
! on S2, G0/1 is the trunk toward S1
4

Create the VLANs on both S1 and S2, then assign the access ports according to your lab's port plan.

Trunking

R1#
interface g0/0/1
 no shutdown
interface g0/0/1.10
 encapsulation dot1Q 10
 ip address 172.16.10.1 255.255.255.0
interface g0/0/1.20
 encapsulation dot1Q 20
 ip address 172.16.20.1 255.255.255.0
interface g0/0/1.30
 encapsulation dot1Q 30
 ip address 172.16.30.1 255.255.255.0

Configure the R1↔S1 and S1↔S2 links as trunks, allowing only the VLANs you route.

5

Subinterfaces on R1

Create one subinterface per VLAN with matching encapsulation, and keep the physical interface in no shutdown.

R1#
show vlan brief            ! VLANs exist + ports assigned
show interfaces trunk      ! trunks up, allowed VLANs correct
show ip interface brief    ! subinterfaces up/up with IPs
show interfaces g0/0/1.10  ! encapsulation correct

Common Pitfalls