Take a look at the following lab:

Final Lab Example


  1. Network at Puntarenas (left) requires addresses for 58 hosts max, this is a startup company, so we will require additional addresses for a future expansion.
  2. Network at Alajuela (right) requires addresses for their current 22 hosts, there is no room for expansion. The clients are located in two different building sections.
  3. Provide an optimal IP scheme to supply both network and router point to point connections.
  4. All communication should work at full speed and full duplex.
  5. Telnet is not allowed for router/switch administration.
  6. SSH version 2 connections should be used.
  7. Connections to routers and switches should be terminated after a certain period of inactivity.

At the end of the example, clients at Alajuela can do www.puntarenas.com and ping any resources on that network (and viceversa).

All routers and switches are using port security and SSH-only connections with extensive login control.

Additional services to configure:

  1. DNS Servers in both offices
  2. NTP and FTP server on Puntarenas Office
  3. All routers should pull date/time from the NTP service
  4. Routers must provide a DHCP service for their office clients.
  5. Port Security must be enables on Switches.
  6. Unused Switch ports must be turned off


First, we need to supply the biggest network, 58 hosts (2^6 = 64, 64 – 2, 62 valid hosts), We need 6 bits for hosts and we are going to take 2 for subnet

192.168.1.|00000000 /24 (original network)

Now we need to supply the network with 22 hosts (2^5 = 32 , 32-2, 30 valid hosts) We need 5 bits for hosts and 3 for subnet

Finally we need just 1 subnet for the point to point connection, we need two bits for hosts (2^2=4, 4-2, 2 valid hosts) and 3 more bits for subnets (that’s 6 in total for subnet), in short it will be:

Note: Pay special attention in how I’m handling the | symbol when taking bits for subnets.

IP assignation for Puntarenas

Device Name Interface IP/Mask
RPun G0/0 /
Serial 0/1/0 /
SWPun Vlan1 /
www.puntarenas.com eth0 /
DNS eth0 /
NTP-FTP eth0 /

IP assignation for Alajuela

Device Name Interface IP/Mask
RALA G0/0 /
Serial 0/1/0 /
SWALA Vlan1 /
www.alajuela.com eth0 /
DNS eth0 /
Client1 to Client18 eth0 DHCP CLIENT

SSH Credentials

Device Username Password
RPun puntarenasrouter puntarenas
SWPun puntarenas puntarenas
RALA alajuelarouter alajuela
SWAla alajuela alajuela

Global Cisco settings

User EXEC Mode cisco (overridden when using SSH)
Privileged EXEC Mode class

Download lab from here.

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Carlos Alberto Umanzor Arguedas

Web Developer at carlosumanzor.com
Web Developer, QA Engineer and Gamer Enthusiast, Developer of Linkcrawler and Father of a future computer ninja.
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