Before we can dive into the details of the CCNA, we have first to build our foundations. We have to know what a network is and how communication flows from one end of the network to the other. We also have to identify the different network components and how they interconnect. The OSI Reference Model is a conceptual framework of how communication takes place in the network.
Just like PCs, smartphones, and every other electronic device, Cisco network devices also need an Operating System (OS) called Cisco IOS to work. The Cisco devices also come with an initial configuration that can be modified to meet our needs. These IOS configurations can be entered through the Command Line Interface (CLI) and saved on the device. We can also back up the configurations as well. Cisco switches and routers operate on different layers of the OSI model. Each device sends the data packet differently. However, they both interoperate with one another.
IPv4 addresses are getting scarce, and subnetting is one of the solutions to alleviate this shortage. With subnetting, a large block of IP addresses is divided into subnetworks which can be allocated to a portion of your Local Area Network (LAN). The IP addresses are configured into the end hosts, servers, routers, and switches for them to be able to communicate in the network. IP addresses can also be allocated automatically using a DHCP server.
Data is transmitted going up and down the OSI layers. From the host PC, the data goes through switch/es before it reaches its destination. If the data is going to another network, a router is needed to route the traffic and reach the destination network. The routes can either be static or dynamic. Static routes are manually configured, and dynamic routes use routing protocols, such as RIP, EIGRP, and OSPF, to determine the route.
Networks can grow over time, and we want our networks to be future-proof and accommodate expansion. Virtual LANs (VLANs) are created to segment a switch, and each segment or VLAN can be assigned a network. Using VLANs doesn’t only improve the efficiency of the network. It also enhances security and performance. Moreover, routing is possible between VLANs, so different VLANs can exchange traffic with one another.
Redundancy is significant for the network. It prevents single point of failure and implements failovers on the network. Redundancy enhances the availability and reliability of the network. However, loops can also occur because of this. Layer 2 loops can be prevented through Spanning Tree Protocol (STP). It blocks a port to prevent a loop from forming. EtherChannel is also used to avoid loops while using multiple physical links. This is possible by grouping the physical links into a single logical link.
Now, after setting the devices up, the devices must also be hardened to make sure that they are protected from attacks from the users inside and outside the network. Switches and routers are designed to forward traffic, so we have to make sure that the traffic being forwarded is not hindered in any way by some security breach.
There are two different ways to utilize access controllers. We can use them for classification and filtering. An Access Control List (ACL) can be used for packet filtering on our Cisco routers and switches. We can specify which traffic is permitted and denied to pass through the device.
ACLs are also used in Network Address Translation (NAT). NAT is also one of the solutions to IPv4 exhaustion. It enables the private IP addresses to be translated to public address/es. ACL is used to identify the traffic that will be translated using NAT.
The future of IP addressing, IPv6, is also tackled here. Its features, how it works, and the configuration is covered in detail. Local Area Networks can be connected to form a Wide Area Network (WAN). For example, offices that are located in different countries are connected via WAN. Various methods and technology can be utilized for connectivity, such as leased lines, DSL, etc.
The extensive network setup would require a significant amount of time and effort to monitor and manage every device in the network. However, network management tools like Syslog and Simple Network Management Protocol (SNMP) helps in the management of the network. They inform us what is going on in the network.
Networks and network devices are not necessarily connected through cables physically. Wireless LANs (WLANs) works by connecting via frequencies. This enables our wireless devices like smartphones and laptops to be connected to the network as well.
In the end, don’t forget to test your skills and knowledge with our Cisco practice tests.
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