Month: April 2012

Linux CentOS – Routing Table Configuration

You may use the following method to add a static route to the routing table of a Linux server using the command line. The server in this example is running CentOS 5.5 64 bit. I have decided to create a static route to Google.com but before doing so I need to find the Internet Protocol…


Networking – Subnetting Practice

If you ever need to practice your subnetting you may use the following website http://www.subnetting.org/. The website contains numerous subnetting questions that will allow you to test yourself periodically. If you don’t find yourself subnetting every day you may use that website for about fifteen minutes each day to be certain that you don’t forget how…


Cisco – Building a Host Table on a Router or Switch

In this example there is a router with a hostname of “router-2″ that has a serial interface configured with the Internet Protocol (IP) address of 172.16.4.2. Without an entry in the host table of the router or a Domain Name System (DNS) server I cannot use the hostname of the router in order to ping…


Cisco – Configuring Static Routes

You may use the following method to add a static route to the routing table of a Cisco router. Before configuring the static route(s) you may run the following commands in order to get a better idea of the network(s) configured on the existing router. router-1#show ip route Codes: C – connected, S – static,…


Cisco – Troubleshooting Static Routes

The following example is utilizing two Cisco 2500 series routers with two serial interfaces and two ethernet interfaces. I created a lab Wide Area Network (WAN) in order to configure static routes on Cisco routers. My goal was to create a static route from the ethernet interface (172.16.3.1) on router-1 to reach the ethernet interface…


Cisco – Performing a Password Reset on a Cisco Router

If you ever find yourself locked out of a Cisco router because you forgot the enable secret (privileged mode) password you may use the following steps to perform a password recovery on the Cisco device. The router in this example is 1700 series Cisco router. 1. Press ctrl+break during the boot sequence and enter ROM…


Domain Name System – Propagation

If you ever update Domain Name System (DNS) records on a DNS server you may use the following method to verify that the updated record(s) are propagating to all internet DNS servers. The server in this example is utilizing Linux CentOS-5.5 64bit. The command you may use is the following “nslookup” and the manual reveals…


Cisco – Configuring a Wide Area Network (WAN) and Telnet

You may use the following commands to configure a Wide Area Network (WAN) between two Cisco routers in a lab environment. The routers in this example are Cisco 2501 routers. Also, I will print the output from the “router-1″ router and you may mirror these configurations on the “router-2″ router (I will note any exceptions…


Cisco – Configure a Description on a Cisco Interface

You may use the following commands to configure a description on a Cisco router or switch. Please note that this will not affect the performance of the router or switch but I recommend doing this for easier administration. ===BEFORE=== router-1#show running-config interface FastEthernet0 Building configuration… Current configuration : 68 bytes ! interface FastEthernet0 no ip…


Cisco – Configuring a Dynamic Host Configuration Protocol (DHCP) Server

You may use the following commands to configure a DHCP server on a Cisco router. The router in this example is a non-ISR 1720 Cisco router being run on Graphic Network Simulator 3 (GNS3). This configuration will name the pool of Internet Protocol (IP) addresses as Marketing, assign an IP address, subnet mask, default gateway,…