Layer 3 Switching 1

certskills
By certskills July 18, 2016 09:05

This next lab asks you to enable layer 3 switching in a couple of distribution layer switches. This lab is pretty far reaching as well, asking for some VLAN trunking configuration and VLAN creation. Because it is such a comprehensive lab, rather than the usual 5-10 minute exercise, plan on 15 minutes to do this one in a text editor. Dig in and enjoy!

Requirements

In this design, you will create the routing configuration required to support four user VLANs. Two user VLANs exist on switch Access1 (VLANs 10 and 20), and two user VLANs exist on switch Access2 (VLANs 30 and 40). The two distribution switches route between those VLANs, using a link between the two switches to route packets between the distribution switches.

The specific rules for this lab are:

  • Configure the access switches (Access1 and Access2):
    • As layer 2 switches
    • Create the necessary VLANs per the figure
    • Assume VTP Transparent mode is in use on all switches
    • Configure the ports on the bottom of the access switches (in the figure) to be access ports in the listed VLANs
  • Configure trunks:
    • Make the link from switch Dist1 to Access1 a manual 802.1Q trunk
    • Make the link from switch Dist2 to Access2 a manual 802.1Q trunk
    • (Do NOT make the Dist1 to Dist2 link a trunk)
  • Configure the distribution switches (Dist1 and Dist2)
    • As layer 3 switches
    • Use SVIs for the switches’ layer 3 interfaces (that is, VLAN interfaces)
    • Use the IP addresses listed in the figure
    • Create the necessary VLANs per the figure
    • Assume VTP transparent mode
  • Configure the link between the distribution switches
    • Do not trunk on this link
    • Make this link an access link in VLAN 50
    • Route between switches Dist1 and Dist2 over this link between the switches
  • Administratively enable all SVI/VLAN interfaces
  • Note that RIPv2 has been pre-configured in preparation for your layer 3 switching configuration

 

Figure 1: Switch Square Topology

 

Initial Configuration

Examples 1, 2, 3 and 4 shows the beginning configuration state of Dist1, Dist2, Access1 and Access2.

 

Example 1: Dist1 Config

 

Example 2: Dist2 Config

 

Example 3: Access1 Config

 

Example 4: Access2 Config

 

Answer on Paper, or Maybe Test in Lab

Next, write your answer on paper. Or if you have some real gear, or other tools, configure the lab with those tools.

To test your solution if you happen to try it with VIRL or real gear, you can check using a couple of different commands. On the Distribution switches check that the VLANs have been created by using the show vlan brief command, then check that the VLAN interfaces were configured with the show ip interfaces brief and/or show running-config commands. Also check that the trunks are operational using the show interfaces trunk command. On the Access switches, check that the VLANs have been created and assigned properly using the show vlan brief command and verify that the trunks are operational using the show interfaces trunk command.

 

Do this Lab with Cisco’s VIRL

You can do these labs on paper and still get a lot out of the lab. As an extra help, we have added files for the Virtual Internet Routing Lab (VIRL) software as well. The .VIRL file found here is a file that when used with VIRL will load a lab topology similar to this lab’s topology, with the initial configuration shown in the lab as well. This section lists any differences between the lab exercise and the .VIRL file’s topology and configuration.

Download this lab’s VIRL file!

All interfaces in topology match the lab figure. The VIRL topology also includes hosts to allow testing of the design. For instance, you can ping between the four PCs to test your configuration.

Configuration Note:

If you do use VIRL, note that to make trunking work, you need to also choose the trunking protocol with the switchport trunk encapsulation dot1q interface subcommand. The VIRL switch IOS image happens to be based on a Cisco switch that supports both the older ISL and the new 802.1Q, so you have to specify which protocol to use.

Host device info:

This table lists host information pre-configured in VIRL, information that might not be required by the lab but may be useful to you.

Device IP Address Gateway User/password
PC1 10.10.10.2 10.10.10.1 cisco/cisco
PC2 10.10.20.2 10.10.20.1 cisco/cisco
PC3 10.10.30.2 10.10.30.1 cisco/cisco
PC4 10.10.40.2 10.10.40.1 cisco/cisco

 

Handy Host Commands:

To see PC IP address: ifconfig eth1

Ping example: ping -c 4 10.1.1.1

Trace example: tracepath 10.1.1.1

To connect to another node within the topology: telnet 10.1.1.1

Answers: PAT w/ a Pool 1
PPP over Ethernet 2
certskills
By certskills July 18, 2016 09:05
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1 Comment

  1. Mit September 15, 03:49

    Hi Wendell,

    Can you please briefly tell why we really need to have Routers when we are already having L3 switches available.

    As it turns out, the Multi-layer switches are faster when it comes to routing mechanisms since the same is hardware based, unlike traditional routers. There must be reason(s) which I am not having a clue of why we can’t replace the existence of Routers with ML Switches.

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