Before we can start to explain how routing protocols work, we need an understanding of wildcard masks. The concept of wildcard mask is one that many people struggle with at first, but with a little time and practice it’s becomes second nature. Converting a full class subnet mask into a wildcard mask quite straight […]
The Cisco administrative distance is a value assigned to all routing protocols to define how trustworthy the information is. If a Cisco router has multiple routes in its routing table for the same network, it looks to see which route has the lowest cost/metric value. The problem with using cost values is that different […]
In yesterday’s post ‘Static Routing’ we saw that we needed to create a static route to allow the Cisco router “AOIP.ORG” to ping “R2”. The static route that we created was ‘ip route 10.0.1.0 255.255.255.0 192.168.1.1’ and ping was successful to the IP address 10.0.1.2 (R2’s Serial interface). The problem with that configuration was that […]
A router by default only knows about networks that are directly connected to it. If a router is not directly connected to the final destination subnet, then the router needs to learn, or be told how to get to that destination. Learning routes can take place through the use of routing protocols, however in […]
In order to set up an IP address on an interface, we need to be in the interface level of the command line. This is a level within the global configuration level. From global configuration mode, we can enter the ‘interface serial 1/0’ command. If you are unsure of what interfaces are on the router, […]
Every Cisco device has 2 sets of configurations. On routers and switches these configurations are called ‘running-config’ and ‘startup-config’ When you make any changed on a router or switch, the change applies to the running-configuration and will affect the router or switch with immediate effect. However, if the device is reloaded for whatever reason, all […]
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 ‘|’ 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 […]
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 […]
By default a Cisco device does not have any passwords on it, so access to the console is open by default, and anyone connecting to the device is able to access privileged mode (enable mode). This of course is a security risk and one of the first things that should be done with a new […]
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 […]
So as we have seen in the post Class-full IP addresses, IP addresses are usually put into Class A,B or C. We have also seen that in 1990 CIDR was invented which allowed us to use Classless addresses for routing, and also saving of address spaces. So what is class-less then? If we have […]