How to configure a Router-on-a-Stick?

[MasonCa]

I am a student, and learning Switching, Routing, and Wireless Essentials

I have a question about configure a Router-on-a-Stick routing

As we can see, We have 5vlans and 3 switch. I configure etherchannel between S1 and S2.

How can I configure the Router-on-a-Stick in S1 S2 and S3?

(The address table may miss some ip, We can give an ip.)

[Seb Rupik · Accepted solution]

Hi there,

Try the following config. You will need to adjust the interface IDs to suit your existing topology:

!! R1
int fa0/1
  no shut
int fa0/1.10
  encapsulation dot1q 10
  ip address 10.0.10.254 255.255.255.0
int fa0/1.20
  encapsulation dot1q 20
  ip address 10.0.20.254 255.255.255.0
int fa0/1.30
  encapsulation dot1q 30
  ip address 10.0.30.254 255.255.255.0
int fa0/1.40
  encapsulation dot1q 40
  ip address 10.0.40.254 255.255.255.0
int fa0/1.50
  encapsulation dot1q 50
  ip address 10.0.50.254 255.255.255.0
!

!! S1
!
vlan 10
vlan 20
vlan 30
vlan 40
vlan 50
!
int gi1/0/3
  desc connected to R1
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!
int gi1/0/4 
  desc connected to S3
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!
int po1
  desc PO to S2
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!
spanning-tree vlan 10,20,30,40,50 priorty 4096
!

!! S2
!
vlan 10
vlan 20
vlan 30
vlan 40
vlan 50
!
int gi1/0/3
  desc connected to S3
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!
int po1
  desc PO to S1
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!

!! S3
!
vlan 10
vlan 20
vlan 30
vlan 40
vlan 50
!
int gi1/0/1
  desc connected to S1
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!
int gi1/0/2
  desc connected to S2
  switchoirt mode trunk
  switchport trunk allowed vlan 10,20,30,40,50
  no shut
!

cheers,

Seb.

[MasonCa]

Thanks, it is very useful. But I still have a question. For R1 and R2, if R1 has a loopback interface which Ip address is 209.165.200.12 /24. If both PC need to ping the loopback interface, how should I configure R1 and R2 with static routes. I guess on R2 I can use static host routes and static routes for R1. Is that correct？

[Seb Rupik]

Hi there,

I have just noticed in my config example, where I had R1 I actually meant R2....hopefully you noticed that. 

Regarding your routing question...

On R2 you should probably configure a static route:

!! R2
ip route 0.0.0.0 0.0.0.0 <R1_serial_int_ip_address>
!

Then on R1 you need a static route directing traffic to R2 for its connected subnets:

!! R1
ip route 10.0.10.0 255.255.255.0 <R1_serial_int_ip_address>
ip route 10.0.20.0 255.255.255.0 <R1_serial_int_ip_address>
ip route 10.0.30.0 255.255.255.0 <R1_serial_int_ip_address>
ip route 10.0.40.0 255.255.255.0 <R1_serial_int_ip_address>
ip route 10.0.50.0 255.255.255.0 <R1_serial_int_ip_address>
!

cheers,

Seb.