AAA TACACS+ and RADIUS TutorialOctober 18th, 2018in CCNA KnowledgeNowadays, security plays an important role in a company. Without any security solution implementation on our network, a user can simply “plug and play” into our network. The user may simple pick up a valid IP address or be assigned one automatically via DHCP. It is convenient, but not a good way if your network contains sensitive data. Worse, this user may have all the rights to your network so he can do dangerous things.When your company grows bigger and bigger, there is a moment that you need to consider implementing security to your network. There are many ways to secure a network but AAA offers a complete solution. In this tutorial let’s find out about this security feature.Before diving into AAA, let’s take an example of a user who wants to connect to our network.READ MORE…GRE Tunnel TutorialApril 26th, 2018in CCNA KnowledgeGRE stands for Generic Routing Encapsulation, which is a very simple form of tunneling. With GRE we can easily create a virtual link between routers and allow them to be directly connected, even if they physically aren’t. Let’s have a look at the topology below:Suppose R1 and R2 are routers at two far ends of our company. They are connected to two computers who want to communicate. Although R1 and R2 are not physically connected to each other but with GRE Tunnel, they appear to be! This is great when you have multiple end points and don’t care the path between them. The routing tables of two routers show that they are directly connected via GRE Tunnel.READ MORE…Basic MPLS TutorialFebruary 23rd, 2018in CCNA KnowledgeMPLS is a new forwarding mechanism called “label switching” in which packets are forwarded based on labels. However, hosts are unaware about labeled packets so routers will need to add a label when entering “MPLS area” and remove that label after leaving there.The idea of label switching is to have only the first router do an IP lookup and assign a label, then all future routes in the network can “cheat” by doing exact match “switching” based on a label. This would reduce load on the core routers, where high-performance was the most difficult to achieve, and distribute the routing lookups across lower speed edge routers.In a traditional IP network:* Each router performs an IP lookup (“routing”), determines a next-hop based on its routing table, and forwards the packet to that next-hop.* Rinse and repeat for every router, each making its own independent routing decisions, until the final destination is reached.MPLS does “label switching” instead:* The first device does a routing lookup, just like before.* But instead of finding a next-hop, it finds the final destination router.* And it finds a pre-determined path from “here” to that final router.* The router applies a “label” (or “shim”) based on this information.* Future routers use the label to route the tr