UCS413 Lab 7 Solution

Network Programming Laboratory (UCS413)
Assignment: 7


Task 1: Learn about the working so the following network component and study the packet transmission with each component using Simulation mode.
a) Switch
b) Router

Task 2: Create following simple VLANs network using GNS3/Packet Tracer.




Steps to Create VLANs

1. In Cisco Packet Tracer, create the network topology as shown below:





2. Create 2 VLANs on the switch: VLAN 10 and VLAN 20. You can give them custom names.

Switch#config terminal
Switch(config)#vlan 10
Switch(config-vlan)#name SALES
Switch(config-vlan)#vlan 20
Switch(config-vlan)#name IT


3. Assign switch ports to the VLANs. Remember each VLAN is viewed as separate broadcast domain.

And just before you configure, have in mind that switch ports could be either access or trunk.
• A trunk port on the other hand is a port that can be connected to another switch or router. This
port can carry traffic of multiple VLANs.


Switch Interface fa0/5 will be configured as trunk port, as it will be used to carry traffic between the two VLANs via the router.

Switch>enable
Switch#config terminal


Switch(config)#int fa0/1

Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 10


Switch(config-if)#int fa0/2

Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 10


Switch(config-if)#int fa0/3

Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 20
Switch(config-if)#switchport access vlan 20

Worth noting: We could have configured all the above interfaces as access ports using interface range command as shown below:

Switch(config-if)#int range fa0/1-4
Switch(config-if-range)#switchport mode access
In the above commands, we have specified an interface range and then proceeded to configure all the ports specified as access ports. Interface fa0/5 is configured as trunk and will be used to for inter-VLAN communication.

Switch(config)#int fa 0/5

Switch(config-if)#switchport mode trunk The next thing is to:

4 . Assign static IP addresses to the four PCs which are located in the separate VLANs. PC1 and PC2 fall in VLAN 10 while PC3 and PC4 fall in VLAN 20.
PC1 IP address 192.168.1.10 Subnet mask 255.255.255.0 Default gateway 192.168.1.1PC2: IP address 192.168.1.20 Subnet mask 255.255.255.0 Default gateway 192.168.1.1 PC3: IP address 192.168.2.10 Subnet mask 255.255.255.0 Default gateway 192.168.2.1 PC4: IP address 192.168.2.20 Subnet mask 255.255.255.0 Default gateway 192.168.2.1

And now it’s very clear that we treat a VLAN just like a physical LAN when assigning IP addresses.
At this point let’s try to test connectivity within VLANs and between VLANs
To test communication between hosts in the same VLAN:
Ping PC2 from PC1 both in VLAN 10. Ping test should be successful.
To test connectivity between hosts in different VLANs:
Ping PC3 in VLAN 20 from PC1 in VLAN 10. Ping here will definitely fail. Why?
Because inter-VLAN routing is not yet enabled. Hope you can see how we’ve used VLANs
to place the hosts into two logical networks which can be viewed as separate broadcast domains.

Now, in order to allow the hosts in the two VLANs to communicate, we need to do something extra. And you can guess what. We’ll configure the router to permit inter-VLAN communication. Let’s do that right away.

5. Configure inter-VLAN routing on the router

We’ll configure the router so that it will enable communication between the two vlans via a single physical interface. How is this made possible? We’ll divide the single physical interface on the router into logical interfaces (sub interfaces). Each sub-interface will then serve as a default gateway for each of the VLANs. This scenario is called router on a stick (R.O.A.S) and will allow the VLANs to communicate through the single physical interface.
Wort noting: We can’t assign an IP address to the router’s physical interface that we have subdivided into logical sub-interfaces. We’ll instead assign IP addresses to the sub interfaces. So let’s do router configurations:

Router>enable
Router#config terminal


Router(config)#int fa0/0
Router(config-if)#no shutdown


Router(config-if)#int fa0/0.10

Router(config-subif)#encapsulation dot1q 10

Router(config-subif)#ip add 192.168.1.1 255.255.255.0
Router(config-subif)#
Router(config-subif)#encapsulation dot1q 20

Router(config-subif)#ip add 192.168.2.1 255.255.255.0

As you can notice from above, the routers physical interface fa0/0 was subdivided into two sub-interfaces( fa0/0.10 and fa0/0.20) , which are then configured as trunk interfaces and given IP addresses. Finally,
6. Test inter-VLAN connectivity.

Here we’ll test connectivity between computers in different VLANs . Don’t forget that its the router that enables inter-VLAN routing.

Ping PC3 in VLAN 20 from PC1 in VLAN 10. If everything is well configured, then ping should work perfectly.

And that’s all!


How to Create & Show VLAN in GNS3
Configuring VLAN Cisco Catalyst, Cisco Catalyst 29XX,37xx,38XX in GNS3 is slightly different than conventional VLAN configuration in Cisco ios following pictures are showing configure and show commands on VLAN(Virtual Local Area Network) in Cisco Catalyst 29XX GNS3 Ios image.

SW1#show vlan
% Ambiguous command: “show vlan “

SW1#show vlan-switch

SW1#vlan database
SW1(vlan)#vlan
SW1(vlan)#vlan 100 name Sales
VLAN 100 modified:
Name: Sales
SW1(vlan)#

SW1#show vlan-switch