Need some advice on learning networking

[BillyCarpenter]

Re: Need some advice on learning networking

I continue to dig deeper into the world of networking but no matter which way I turn, all roads lead back to the OSI model. A couple of month ago I hadn't even heard of the OSI model but after studying up on it, it kinda made sense to me. Sorta. Well, by using WireShark the lightbulb finally came on for me. It's much easier to grasp the OSI model when you can actually see every step of the process. At least for me.

One thing that I recently grasped is that everything above the "Data Link Layer" (Layer 2) is all software, if you think about it - there's nothing to touch. It's all software. And even part of the Data Link Layer is software as it's divided up in 2 parts: (1. The actual physical connection. (2. Logical Link Control -- which sends the data up the OSI model.

Once you get above the Data Link Layer you're dealing with protocols (and a bunch of 'em) and data packets.

Troubleshooting the physical layer seems fairly simple and straight forward. And kinda boring if you ask me. Where the fun comes in at is anything above Layer 2.

The challenge when troubleshooting above Layer 2 is you must learn every protocol that you're trying to troubleshoot. And I'm not talking about learning in theory only. You actually must learn every single step of the protocol. I'm talking about things like the 3-way handhake and things like that.

Just some random thoughts....

[BillyCarpenter]

Re: Need some advice on learning networking

Further down the rabbit hole I go....

I decided to capture DNS data on Wireshark but first I watched a video. The guy in the video starts talking about loopbacks and Spanning Tree Protocol. I've never heard of these so I have to watch 2 more videos to learn about each. And that led to me another video about switches.

Here's what I gathered. Let's start with switches:

Switches have something called a Mac Address Table. More on that later. Many networks are set up using "multiple" switches for "redundancy". In other words, if one switch goes down, the network still performs. The problem with using multiple switches is that it can cause a "loopback." To guard against a loopback, that's where Spanning Tree Protocol comes in. Spanning Tree helps prevent loopbacks. If the Spanning Tree protocol becomes corrupt, you can still have a DNS (or other types of loopbacks) loopback and it can cause the entire network to crash.

PS - I also learned that I can resolve a hostname to an IP address by first flushing the DNS server and then doing the following:

Example: nslookup yahoo.com 8.8.8.8 This forces the computer to go outside if it's DNS cache and go to the google server for the DNS record.


That's all for now and my head really hurts.

[KenB]

Re: Need some advice on learning networking

Further down the rabbit hole I go....

I decided to capture DNS data on Wireshark but first I watched a video. The guy in the video starts talking about loopbacks and Spanning Tree Protocol. I've never heard of these so I have to watch 2 more videos to learn about each. And that led to me another video about switches.

Here's what I gathered. Let's start with switches:

Switches have something called a Mac Address Table. More on that later. Many networks are set up using "multiple" switches for "redundancy". In other words, if one switch goes down, the network still performs. The problem with using multiple switches is that it can cause a "loopback." To guard against a loopback, that's where Spanning Tree Protocol comes in. Spanning Tree helps prevent loopbacks. If the Spanning Tree protocol becomes corrupt, you can still have a DNS (or other types of loopbacks) loopback and it can cause the entire network to crash.

PS - I also learned that I can resolve a hostname to an IP address by first flushing the DNS server and then doing the following:

Example: nslookup yahoo.com 8.8.8.8 This forces the computer to go outside if it's DNS cache and go to the google server for the DNS record.


That's all for now and my head really hurts.

I doubt that it's true any more, but the early Canon MFPs (like the iR5000) got a little weird if Spanning Tree was turned on. They could also get a little wiggy with PoE (Power over Ethernet).

It was normally one of the first things the help desk would ask you to check. I also remember a number of tech pubs that said the same.

[slimslob]

Re: Need some advice on learning networking

Further down the rabbit hole I go....

I decided to capture DNS data on Wireshark but first I watched a video. The guy in the video starts talking about loopbacks and Spanning Tree Protocol. I've never heard of these so I have to watch 2 more videos to learn about each. And that led to me another video about switches.

Here's what I gathered. Let's start with switches:

Switches have something called a Mac Address Table. More on that later. Many networks are set up using "multiple" switches for "redundancy". In other words, if one switch goes down, the network still performs. The problem with using multiple switches is that it can cause a "loopback." To guard against a loopback, that's where Spanning Tree Protocol comes in. Spanning Tree helps prevent loopbacks. If the Spanning Tree protocol becomes corrupt, you can still have a DNS (or other types of loopbacks) loopback and it can cause the entire network to crash.

PS - I also learned that I can resolve a hostname to an IP address by first flushing the DNS server and then doing the following:

Example: nslookup yahoo.com 8.8.8.8 This forces the computer to go outside if it's DNS cache and go to the google server for the DNS record.


That's all for now and my head really hurts.

8.8.8.8 is one of Google's public DNS servers. The other is 8.8.4.4. There are a number of other similar DNS servers out there. 5 Best DNS Servers (2020) - Free Public DNS For Speedy Connections

[BillyCarpenter]

Re: Need some advice on learning networking

I think I have a firm grasp on this now.

First things first. Unless a company is using multiple switches set up for redundancy, there's no need to worry about loopbacks or STP (Spanning Tree Protocol) But f they are running multiple switches it could cause problems when setting up a copier.

Here's what happens. Each switch has a Mac Address Table. That's how the switch is able to send data to the correct device. When a loopback occurs the MAC Address Table of the switch becomes corrupted and the data meant for the copier gets sent to the wrong port.

How do you determine if this is happening? One way is to use WireShark. When there's a loopback you will see repeat multiple requests for the same thing.

I hope I explained that well enough to understand. I barely understand it myself.

[bsm2]

Re: Need some advice on learning networking

Network +

http://dl.amirkabir-science.com/book-paper/network/Networkplus-2018.pdf

[BillyCarpenter]

Re: Need some advice on learning networking

I just used WireShark to capture DNS when scanning from a Kyocera copier. The DNS settings on the copier are 8.8.8.8 - Google DNS server. I didn't flush my DNS record before scanning so it used the DNS cache of my AT&T router. The hostname of the copier is KMD35358.

See image below:

DNS capture.JPG

[BillyCarpenter]

Re: Need some advice on learning networking

I was playing around with WireShark I something showed: doubleclick.net

I looked it up. Here's what it is. I don't like that.


doubleclick.net

is the domain used by Google for their advertising services company, DoubleClick. The domain is used for many purposes, including online advertising and tracking users behavior.

[tonerhead]

Re: Need some advice on learning networking

I know scary stuff ain't it. G0091e knows everything about everyone. People buy and sell your personal data daily. Discover the dark web, I did years ago. You can browse without being traced. Many people consider the dark web to be evil, the press and television definitely portrait it in that fashion. Yes, like guns and knives it can be used for good or evil. You can kill someone with a knife or you can open boxes, slice bread, cut cheese, doctors perform surgery. I have some medical conditions that I don't want G009le to know about, I can research in private on the dark web. I like reading on car maintenance and don't want to be overrun with spam, etc. I don't use it to buy drugs, look at porn, etc. It is a tool.

Here is a link to one of the better ones. If you know how to make bootable flash drives using iso's, give it a try. Hint don't use anything less than USB 3.0 for flashdrive too slow otherwise and you won't like it.

Tails - Download and install Tails

P.S. I used to do my online banking and purchasing with this years ago, but many places will not allow this anymore. They block dark web browsing into their sites. So for these I am using a non-persistant linux on a flash drive and just upgrade the flashdrive as needed. Being non-persistant you get a clean operating system everytime you boot from it. Free of cookies, traces, history, etc.

Paranoia will destroy ya (as the song goes)

[slimslob]

Re: Need some advice on learning networking

I know scary stuff ain't it. G0091e knows everything about everyone. People buy and sell your personal data daily. Discover the dark web, I did years ago. You can browse without being traced. Many people consider the dark web to be evil, the press and television definitely portrait it in that fashion.

Of course the press and television portray it as evil. It prevents them from being able to track you. And then you have all those that want you to use their VPN to browse 'anonymously' They don't tell you that they still are tracking your browsing. I tried to use Anonymizer 14 years ago. Army.mil would not allow me to connect to my military email account through it.

[BillyCarpenter]

Re: Need some advice on learning networking

This morning I installed Windows Server 19 as a virtual machine. The first thing I noticed is that I could ping any device on the network from the server but couldn't ping the server from another device. I think I know the setting to allow other devices to ping the server but I'll get around to that later.

At the moment all I want to do is set up a shared folder on the server and scan a document to that folder. Thus far I have failed. I think I need to create a user name and password in the Active Directory for the copier.

The thought of setting up a server excites me but unfortunately this is gonna take a long time to learn.

[slimslob]

Re: Need some advice on learning networking

This morning I installed Windows Server 19 as a virtual machine. The first thing I noticed is that I could ping any device on the network from the server but couldn't ping the server from another device. I think I know the setting to allow other devices to ping the server but I'll get around to that later.

At the moment all I want to do is set up a shared folder on the server and scan a document to that folder. Thus far I have failed. I think I need to create a user name and password in the Active Directory for the copier.

The thought of setting up a server excites me but unfortunately this is gonna take a long time to learn.

Yes as to credentials in Active Directory. You may also need to set up DNS on the server, set that as the first DNS on the MFP and be sure to ad the Domain name to the interface settings of the MFP.

[BillyCarpenter]

Re: Need some advice on learning networking

Yes as to credentials in Active Directory. You may also need to set up DNS on the server, set that as the first DNS on the MFP and be sure to ad the Domain name to the interface settings of the MFP.

Do I need to set the server, my computer and the coper on a domain? Forgive my ignorance. First time doing this.

[slimslob]

Re: Need some advice on learning networking

Do I need to set the server, my computer and the coper on a domain? Forgive my ignorance. First time doing this.

I could be wrong but if you have Active Directory you have a domain. If you set it up as a peer to peer server then there would be no Active Directory.

[bsm2]

Re: Need some advice on learning networking

blind leading Blind

Yes setup a user Basic stuff