Need some advice on learning networking

[BillyCarpenter]

The 2nd course that I'm going thru is much different than the first. This one consists of one lecture after another. And it goes into much greater detail.

CCNA is big on fundamentals and I've covered them twice now. There's a HUGE advantage in going back over something for a 2nd time. If you're like me, you're gonna pick up on some things that you missed the first time around.


Basically what this course is trying to do is to get my mind to think like a computer. That requires a lot of memorization. I've been using flash cards to help commit a lot of this information to memory. I don't think flash cards will ever be outdated.


Anyway, not a lot to update. I've completed about 15% of both courses. I have a long road ahead.

[BillyCarpenter]

Here's a question for the board. I think I know the answer. THINK being the key word here.


So, I configured one of the ports on a router with the following address: 10.10.10.1/24.

I then checked the routing table and it said the following:



10.0.0.0/8 is variably subnetted,
10.10.10.0/24 is directly connected.
10.10.10.1/32 is directly connected.


The key in reading the routing table is to look at the subnet mask. (Hint: what is a 32-bit mask.)

[BillyCarpenter]

Here's a question for the board. I think I know the answer. THINK being the key word here.


So, I configured one of the ports on a router with the following address: 10.10.10.1/24.

I then checked the routing table and it said the following:



10.0.0.0/8 is variably subnetted,
10.10.10.0/24 is directly connected.
10.10.10.1/32 is directly connected.


The key in reading the routing table is to look at the subnet mask. (Hint: what is a 32-bit mask.)

I'm gonna try to explain this:




1.The subnet mask has NOTHING to do with what class of network we'e talking about. IP address 10.10.10.1 with a 255.255.255.0 subnet mask is still a class A network. All we've done is subnet this class A network.


That why the router automatically says that 10.0.0.0/8 has been subnetted 2 times.


The first subnet is 10.1.10.1/24...and the second subnet is 10.10.10.1/32 (a 32 bit mask means that only that IP address is on this subnet. There's no room for another host.)




This had me confused for the longest.

[BillyCarpenter]

A couple of quick notes:


1. This course has spent a lot of time covering subnetting. I now know why they've spent so much time covering it. Here are the reasons:

a.) Network Design: When a network is being designed, there's a lot of mistakes that can be made if you're not subnetting. Needless memory could be wasted on the routers if you're not subnetting properly.


b.) Reading the routing table on a Cisco Router: If you don't understand subnetting, you're not gonna be able to properly read a routing table. That's the bottom line so learn it and learn it well.


On a completely different note: I was moving along just fine in understanding the life of a packet and everything that needs to happen in order for the packet to make it to it's destination. But then they changed the game a bit and added something in LAYER 3 of the OSI model. What did they throw in? FQDN. That stands for FULLY QAULIFITED DOMAIN NAME.

Some applications will place an IP address in the header at layer 3 but some use a FQDN and the name must be resolved before the packet can move forward. I mean, DNS is nothing new but breaking it down on @ the micro-level is new to me. And complex.

[BillyCarpenter]

I was reading back thru the last several posts and I know that no one is interested in what I'm saying except for me. You'll have to forgive me.

I'm posting this stuff as much for me as anyone. I've found that if I can't explain something to someone then I don't really know it myself.


With that in mind, lets talk about ARP.

Personally, I love ARP. Without ARP we wouldn't have computer networking as we know it. ARP is a Layer 2 protocol, which means it deals with MAC ADDRESSES. To further reinforce this point, ARP is a broadcast signal. That means the switch will broadcast out of every port of the switch in an attempt to locate a mac address. That makes ARP a necessary evil. (Remember Broadcast Domains?)

But remember that ARP is a LAYER 2 protocol. That means a router doesn't care about ARP. ARP will be dropped like a hot potato @ the router. It should be noted that while ARP can't get past the router, there is another way to advertise for an unknown device that lives on the other side of the router. We'll save that for another day.

[BillyCarpenter]

Today I took a break from Cisco Routers & Switches. Tracing packets across a network wears you out at some point. Instead, I spent the day on Windows Server 2019. But first I built a new virtual lab using Virtual Box instead of using VMWARE like I had been using. It took a minute to get used to but I like it. Virtual computing is the future, I think. It's pretty fucking amazing.


Anyway, I finally figured out a way to migrate a local user account to a domain account. And I found a very easy way to do it by using a Migration Tool called: ForensiT Free Downloads


It's completely free and oh so easy to use.

[BillyCarpenter]

Welp, I just ordered the server that rthonpm recommended. I still have to order more RAM and a few hard drives. I like to thank rthonpm for his help. He's been great.

[BillyCarpenter]

I'm back at it this morning, working on my CCNA. I had to take a few days off as I was mentally spent. I have a passion for networking but this is complex information to learn and it will exhaust you mentally. Word to the wise.


Today it's all about learning about ports. No, we're not just learning what ports are associated with what protocol. That's not the way it's done at the CCNA level. We must learn it from the OSI Model perspective.


Let me give a brief explanation.


Let's say that I want to go to website: Copytechnet Home

-The first thing that happens is copytechnet.com must be converted to an IP address via DNS.

-After the data is passed from Layer 7, to layer 6 and then layer 5, it finally reaches LAYER 4. Layer 4 is the layer that networkers start to get interested.

- Layer 4 is where UDP or TCP will be added to form part of the segment. But this is also the layer that port numbers are added. There are ports that are referred to as WELL KNOWN PORTS. copytechnet.com is a HTTP site and since HTTP uses a well known port (port 80), my PC knows to add port 80 to the segment at Layer 4. My PC will also randomly add a Source Port for the webserver to send back a reply.

That's pretty much everything that happens at Layer 4.


It all seems simple now but this stuff kicked my ass for a while.


EDIT: If we want to break it down a bit further.....


When my PC sends a request to the server that hosts copytechnet.com it is usually written like this: (copytechnet.com has an IP Address of 173.254.238.186). Yes, I checked for the correct IP Address.

Anyway, it's written like this: 173.254.238.186 : 80: 65512. Notice that the IP address is followed directly by a colon and the number 80 and that's followed by another colon and the number 65512. The first colon is used to separate the IP address from the destination port number of the server and of course 80 is the well know port for HTTP. The second colon is used to identify the source port that the webserver is to use to send info back to my PC. 65512 was a randomly generated port selected by my PC.

Once the webserver receives the requests and sends data back to my PC the segment will be reversed. My public IP address will now be the destination portion of the segment and yada, yada, yada. You get the idea.


EDIT 2: Not only are ports responsible for getting information back to the browser on your PC, it aslo gets it back to the correct tab. In other word, for every tab you have open in your browser, there's another port that was opened for that tab.

[BillyCarpenter]

Question: Why is UDP known as a connectionless protocol and why is TCP known as a connection oriented protocol? No using Google.

[skynet]

Question: Why is UDP known as a connectionless protocol and why is TCP known as a connection oriented protocol? No using Google.

UDP Connectionless Protocol does not involve handshaking between sending and receiving transport layer entities before sending a segment. Hence the name – connectionless.