Archive for the 'Management' Category

NAT (Network Address Translation)

Monday, September 21st, 2009

NAT or Network Address Translation is a key function required in every organisations network. Since all organisation use RFC 1918 IP addressing, and these IP addresses are not allowed to exist on the internet, before we send packets to the internet we need to translate the internal IP address into a useable public IP address. [...]

Configuring Syslog on Cisco Routers

Thursday, July 30th, 2009

As part of any management and audit solution for networking, Syslog is vital.   Syslog messages allow us to track system error messages, exceptions, and other information, such as device configuration changes. It allows for historical reporting, depending on the application keeping the logs, as well as help in fault finding.   Cisco devices support [...]

Configuring DHCP on a Cisco router

Monday, July 20th, 2009

DHCP (Dynamic Host Configuration Protocol) allows a server (in this scenario a Cisco router) to issue IP addresses to computers on the network dynamically. This is not a great solution for servers, which should have static IP addresses, but for client computers needing access to the network quickly and easily, this is certainly a great [...]

IP Host

Wednesday, July 15th, 2009

If you find yourself often connecting to the same devices and are looking a quicker way to telnet to them rather than constantly typing the entire IP address for each one. Or if you have a very large network and find it hard to remember every devices IP address, but you can remember the host [...]

IP Domain-Lookup

Tuesday, July 14th, 2009

Often when typing commands in a hurry, or just typing incorrect commands, Cisco routers will try to do a lookup to find out if the invalid command is the name of another device you are trying to connect to. This results in the router displaying ‘Translating “the command”…domain server (’ three times and not accepting [...]

Banner – Message Of The Day (MOTD)

Wednesday, June 24th, 2009

It is advisable that on all your devices in your network, you have a disclaimer or message that appears when someone connects to your device. There have been many cases over the years where a hacker has gained access, been caught, and got away with it since there was nothing in place informing that they [...]

Using the Pipe ‘|’ command

Tuesday, June 23rd, 2009

Using the Pipe ‘|’ is by far one of the most important things you can learn on a Cisco device. I never really appreciated this command when I started out in Cisco, as it seemed to take me longer to use it, and I didn’t get to see what I was looking for. In hind [...]

The “do” command

Monday, June 22nd, 2009

One of the most annoying things I kept doing when I started out in Cisco, was constantly typing ‘show’ commands when in the wrong level of the configuration. By default, Cisco only allows you to do a ‘show’ command when you are in privileged mode (AOIP.ORG#). This can be frustrating when you are multiple levels [...]

Configuring VTY Access

Wednesday, June 17th, 2009

VTY (Virtual Terminal Lines) are used when you wish to telnet into a router remotely. In order for the router to allow telnet connections, the VTY lines need to be configured with a password, which is not a default setting. If you were to try connect to a router with telnet and the VTY password [...]

Useable IP addresses in private networks

Wednesday, June 10th, 2009

I’m sure you can imagine that trying to administer an IP address for every single person on the internet would be near impossible. Added to the fact that companies don’t want every computer in their network to be accessible on the internet for security reasons. The Internic and IANA (the two governing bodies for IP [...]