Weeks ago and maybe months :), I talked about distance vector protocols and with that you probably got the feeling that when using a distance vector protocol it does not give a full network graphical representation of the entire network. Only the directly connected routes can't remember? Check out this post Distance Vector Routing.
In today's post I wanted to talk about the widely used Ping command. Which is one of the best methods (I think) to begin network troubleshooting. When part of the network goes down it is sometimes hard to figure out why? When you issue the ping command or the extended ping command in a Cisco router several ICMP codes can come up on the router. Let's discuss them!
In a perfect world we would never need redundancy on a network infrastructure, but as you know as well as I know we don't live in a perfect world. Hardware will eventually fail, bottlenecks will appear, and the speed of our network will become slower when we max the bandwidth on links. So having redundancy in routers, connections, and having a hierarchy network is one of best choices to make when improving the efficiently of the network.
Wow July is almost over and I only posted one topic! Before August comes up I wanted to post at least one more topic which deals with the wireless side of the networking world. Ever heard of Super WiFi?
In today's post let's talk about CDP the Cisco Discovery Protocol. This protocol helps us in two ways, it first helps us verify that a connection between router or switch is set up correctly at least up to layer two in the OSI model. This also helps us discover Cisco devices that are in are network and which interfaces these devices are connected too and from are Cisco equipment. The Cisco discovery protocol is Cisco proprietary and before I go any further let me mention that CDP is a security risk because of the detailed information CDP gives out which helps you has a network administrator build a current network infrastructure, this can also hurt you because this information can easily be sniffed by programs that are easily searched on the internet. So what is the purpose of CDP? CDP can gather device information from neighboring switches and routers without the need for a password. Like mentioned before this is great for troubleshooting a problem, discovering new devices that are not documented in your network topology, and verifying that each device is physically connected to the correct interfaces according to network documentation. CDP can discover the following details from neighboring devices that support CDP:
Couple weeks ago I talked about routing protocols and in the post I mentioned two routing protocol features distance vector and link state. Although these protocols fundamentally do the same thing by getting information on remote networks they get this information in a different way. For today let's introduce distance vector routing. With a distance vector routing protocol, a router learns about a route to a different network (that's the purpose of a routing protocol) the router only knows the "distance" to get there this is usually called the metric.
Before the internet and general networking become popular into what it is now, there were and still are routing protocols that only do classful routing. What is classful routing? When I was talking about Dynamic Routing earlier (See the post Dynamic Routing Protocols) I mentioned there was a difference between classful routing and classless routing. So in today's post let's focus on these two but important topics when using routing protocols.
This is a master list of various Cisco IOS commands relevant to the CCNA track, along with brief descriptions of what each command does. Some commands may exceed CCNA requirements but provide valuable information.
Although having a wireless LAN sounds like a wonderful idea, there are things that need to be implemented like security. A wireless LAN can be uncontrollable has it is just radio waves and anybody can receive them. Having and using good security practices can help you be under control of your wireless LAN. Not having any security in a wireless LAN environment will cause anybody to have access to the network. Some threats that lead to wireless LANs can be the following:
