A little off Topic - OpenNMS

While combing through Reddit, I stumbled upon a discussion about ISP and remote monitoring of client endpoints(modems). The highest pinged option was OpenNMS, so I figured I'd take a look.

I've toyed with LibreNMS but gave up because of time and irregular discovery results. It took about 2 hours to fully setup and have SNMP working correctly. Essentially, I followed these rules layed out by OpenNMS documentation to the T. I don't have Notifications working yet, but otherwise, I have my LAN devices showing up.  My PFSense firewall also displays each physical Interface via SNMP.

Examining the Transport Layer

As you're probably noticed I'm skipping over a few sections of the OSI model intentionally. The Transport layer is where I get the most confused, so this blog post is to help myself and all of you (possibly).

The Transport Layer, layer 4 of the OSI model is meant to reliability transfer data by error correction. Two different categories handle this traffic.

• Transmission Control Protocol(TCP) | Connection-oriented - Specific parameters are established before data is sent
• User Datagram Protocol(UDP) | Connectionless - Data sends at best effort, no connection is set before hand.

This seems like a great place to say, let's just stick with TCP right? Well no, in TCP each packet is 

• Connection Establishment(3-Way Handshake..What?)
• Segmented and sequenced to ensure proper data when reassembly has completed.
• Flow Control - transfer rate is negotiated to prevent congestion

You recall workstations and devices having an IP address, correct? While network devices are able to obtain connection to different services and applications. We need to define what traffic is what. The Transport Layer is responsible to determine which OSI layer to divert the packet to depending on this traffic, or port number. 

Service or services are able to run on a single computer, these are determined by port numbers and look like this: www.google.com80. For example, a web hosting server would be using port 80(HTTP) to deliver a website to clients. I'd sure you'll notice we don't type a ":80" after a website that's because browsers by default place HTTP in the front of a website for you. So, in reality: www.google.com, really looks like this: http://www.google.com.

Ports 0-1023 are reserved and are considered, well-known. Ports 1024-49151 are reserved by the IANA upon request. From 49152 - 65536 cannot be registered, and are considered dynamic. Here's a short list of well-known ones:

Remember that 3-Way HandShake business I was talking about? That's what happens during each TCP packet needing to be transferred. For example, let's say Host A needs to access a website from Server B. Before any HTTP(Port80) traffic sends over. An acknowledgement needs to be established, like someone answering a phone call.

• Host A - Sends over a Syn or synchronize message to Server B to initiate a connection
• Server B - Sends back an Acknowledgement or ACK to Host A. Server B also sends over a SYN message to keep the sequence in check. Thus Host A receives a SYN + ACK from Server B.
• Host A - Completes 3-Way Handshake by sending an ACK to Server B's SYN message.

Passive Open - to ensure complete communication to a specific port from the Internet. You may have check a port forward configuration on your firewall, by going to canyouseeme.org. You would supply your public IP address and desired port. If your configuration worked, it would state open.

I've reached my limit on TCP/UDP, further information can of course be found at: https://en.wikipedia.org/wiki/Transport_layer .

My Path to Success, and First Day

Time is a companion that goes with us on a journey. it reminds us to cherish every moment, because it will never come again. ~ Jean Luc Picard (Star Trek Generations) 

Such a great quote from a great movie, I can feel eyes glaring now. Honestly, it's how I paved my way of life. Pushed myself through hard times, with God' help of course. It says you'll never obtain this moment in time ever again, so why waste it? Well, I'm here to help myself and others throughout their Cisco Journey. 

Day 1 - OSI Model, Networking Fundamentals

Before we leap into creating a VLAN, setting up WAN connections, we need to begin with the fundamentals. Personally I dread this part, I want my first day to be creating fancy things that make us look cool. Well, without fundamentals for almost everything, we wouldn't be able to troubleshoot or dig deeper into an issue during that troubleshooting phase. Our coolness would drop if we're asked a simple question we're unsure of. 

If I could direct your attention to a Wiki page for the OSI model. As stated in the first paragraph:

The OSI model is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. (OSI Model (n.d). In Wikipedia. Retrieved December 12, 2015,

from https://en.wikipedia.org/wiki/OSI_model).

This website offers a plethora of information not only on the OSI model, but for other topics throughout our Cisco/CCNA journey. Let's start off and name these models and a short description of each, and possibly some examples:

OSI Model (From Bottom up):

1. Physical Layer- The physical medium between nodes(computers, switches/hubs to computers, phone lines to headset). These connections can range from RJ11, RJ45, even a serial RS232 between a console port in a switch to a USB to serial adapter on a laptop. Before switches became popular, Hubs allows multiple devices to communicate over a network, those devices are part of the Data Link Layer. 
2. Data Link Layer - While bit level communication is traversed over our cable. We need a way to convert this data into something readable by hardware or software. At this layer, these bits are converted into Frames. Two major topics to remember here, the MAC(Media Access Control) and LLC(Logical Link Control). Layer 2 switches operate at this level, VLANs can be created and workstations or switches use ARP to identify IP address to MAC address of a device. 
• MAC addresses are hard coded into a Network interface card, or NIC. Not one device as the same MAC address in the entire world
• LLC is responsible for identifying the network protocols and encapsulation. 
3. Network Layer - Those Frames are now Packets. Now we're getting into IP addresses and Layer 3 Routing. As stated before, MAC addresses are baked into NIC cards. The network layer allows us to use 32-bit (IPv4) or 128-bit(IPv6) addresses, easier for us humans to communicate those values.
4. Transport Layer - responsible for TCP/UDP traffic. Here's you'll be introduced to the 3 Way handshake which initiates a reliable TCP connection between nodes. UDP uses best effort to initiate a connection. Further description of this topic can be found here.
5. Session Layer - After communication has started, there need to be a method to organize this right? Session layer takes care of this. It allows us to create multiple SSL or FTP sessions at one time, without data going to the wrong location.
6. Presentation Layer - Handles character encoding, different file types like GIF translation also encryption and decryption. It's responsible for transforming data into a format an application recognizes. HTML and CSS are also part of this layer. 
7. Application Layer - here's were ports and application specific traffic comes into play. Such as FTP, HTTP, SMTP and others. 

Granted, this information doesn't completely cover the OSI Model, this honestly why my Cisco Journey didn't happen years ago. Memorizing layers 2-4 really put a burden on remembering this stuff, for me at least.

Since taking my Network + in 2010, I've actually retained move of this information, and it's helped me greatly throughout my career. Next time we encounter each-other, I'll digging deeper into TCP/UDP. 

Thanks for joining!

Paving the Future.

Greetings everyone - welcome to my 3rd attempt at Blog creation. Previously mindless topics were embedded into my blogs, mostly old hardware tutorials on how to resurrect an HP tz2000 and install Windows XP..Yea, so 2008.

Now, I'm procuring a blog to assist in my Cisco CCNA R/S journey. Mostly to ensure I keep myself on track, and to help anyone else with their journey. I'm a visual learner, reading books hardly helps, only for obtaining examples. Listening to Udemy videos are better, but I need to witness an example for it to stick into my brain. I'm not a by the book type of person, but I learn much better by example. Thus far, I'm about 75% ready for this exam.

So, what to expect from this blog; Examples risen from Packet Tracer, step by step at changing or creating DHCP, VLANs, or ACLs really anything to help me remember this material. I aim to set scheduled to keep myself and whomever is continually reading this blog on track. Any input or correction is welcome.

Let's get started.