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The Domain Name System does something wonderful and transparent for us: It takes the hostname we enter into a web browser – usually a website’s URL – and translate it into the IP address that’s actually needed to make the communication between host and website happen. A DNS Query is sent out asking for a […]
Before we head back to L3 and start work with routing protocols, let’s take a few minutes to go into more details about the going-on at the Transport Layer(OSI Layer4). TCP and UDP get the job done here, but they do so in wildly different styles. TCP: Guarantees delivery of segments. Performs error detection and […]
Auto negotiation Ports, Ports, Ports By default, Cisco Switch ports are set to automatically negotiate port speed and duplex with the connected partner. Basically the port and the connected device have a conversation about the highest level of speed and duplex each can support, and then come to an agreement about the speed and duplex […]
Before we start, I’ve kept VLAN10 at 10.1.1.2/24. The default gateway and setting and everything else is the same as previous section. Telnet Running on TCP port 23, Telnet is an excellent way to logically hop around a network rather than physically hopping around a network. Even if all the devices you are working with […]
Introducing To SVI While our L2 switches don’t perform routing (they just switch and that’s all they do), we still need an IP address (a L3 address) on that switch in order to remotely connect to said switch.( we want to configure it without actually having to go to the switch , connect to the […]
Introduction to Routing We’ll start our walkthrough with a basic network and follow the decision-making process from the point of view of the host, then router. We’ll start with this iconfig output from our host PC. When a host sends a packet, there are two possibilities regarding the destination host. It’s on the same subnet […]
When one host sends data to another, that data has both a MAC destination address and an IP address and an IP destination ( Layer 2 destination and Layer 3 destination). Up to this point we’ve been working with L2 destination addresses as opposed to L3 destination. We’re now going to move up a layer […]
The Enemies Within It’s easy to think about network security in terms of playing defense from attackers outside our network. Thing is, plenty of successful attacks have been launched from inside a network, utilizing seemingly innocent network services and protocols such as DHCP, ARP, CDP, Telnet, and even VLANs. Port Security A basic Cisco security […]
