IP Addresses 1

By certskills April 29, 2016 09:05

More daily lab practice! This one combines a little bit of subnetting math with IP address configuration. If you know how to calculate the IP addresses in a subnet, and you know how to configure IP addresses, make this one a speed test. See how long it takes you from the point of reading the specifics until you can type the config!


Configure the IP addresses for the LAN interfaces for the routers shown in the figure, per the subnets listed in the figure. The specific rules for this lab are:

  1. Assign the core router’s interfaces with the highest IP address from each subnet
  2. Configure the Branch routers interfaces connected to the Core router with the next highest remaining available IP address in each subnet (after the assignment of the Core router interface IP addresses)
  3. Configure the other interfaces on the Branch routers – the interfaces connected to user PCs – with the highest IP address in each subnet
  • Assumptions:
    • Assume all device interfaces shown in the lab are up and working
    • Assume that the PCs are pre-configured with the correct IP addresses
    • Assume that routing is correctly configured



Figure 1: Simple Hub and Spoke Topology


Initial Configuration

Examples 1, 2, 3 and 4 show the beginning configuration state of Core, Branch1, Branch2 and Branch3.


Example 1: Core Config


Example 2: Branch1 Config


Example 3: Branch2 Config


Example 4: Branch3 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, the easiest way to verify the correct IP address assignment is to move to one of the devices and attempt to ping each of the other devices. You can also verify each of the configured IP addresses on the devices using the show ip interface or show ip interfaces brief commands.


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!

The virl topology matches this lab topology exactly. The host info does as well.

Network Device Info:

All switches in this lab are unmanaged layer 2 switches and the first available links were used to complete the connections.

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 User/password
PC1 cisco/cisco
PC2 cisco/cisco
PC3 cisco/cisco


Handy Host Commands:

To see PC IP address: ifconfig eth1

Ping example: ping -c 4

Trace example: tracepath

To connect to another node within the topology: telnet

Answers: IPv6 Static Routes 1
Answers: IP Addresses 1
By certskills April 29, 2016 09:05
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  1. LT April 8, 07:08

    Regarding the Host Device info table, the PC IP addresses do not match the address configurations of the router interface IP address (except PC1). PC4 does not exist in the topology graphic, nor is there any pre-configurations for this device.

    Reply to this comment
    • CCENTSkills April 8, 08:11

      Ahh, copy/paste error. Fixed the table. host IP addresses are now correct and match the original VIRL file. Thanks for the heads up.

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