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I see. You recommend I buy networklessons course or buy this book?

What kind of labs can I do? And what kind of books to study. THere are cisco books but I could not figure out which one is good. Please tell.

The next screen capture shows the Ethernet portion of the DHCP ack packet.
The Ethernet destination address is FFFFFFFFFFFF, which is the broadcast hard-
ware address, and the Ethernet source address is 005004744FFF, which is the
hardware address of the DHCP server

The DHCP portion of the DHCP ack packet contains information about the IP
address and the lease parameters. The following screen capture shows the DHCP
portion with all the DHCP options. After the DHCP client receives this acknowledg-
ment, then the client has an IP address. Now that the client has a valid lease on an
IP address, the client finishes building its TCP/IP stack.


Taken from TCP/IP foundations by andrew G blank

Let's discuss the "DORA" of DHCP.

1) Discover
Client broadcasts that "I want IP address".
Destination IP address=All 0s.
Destination hardware address=All Fs.
Source hardware address=DHCP Client address

2) Offer

Server/s makes an offer.
Destination hardware address=client's mac address
So that client knows the offer is for it.
It also should contain server's IP address/es.

3) Request

Client broadcasts DHCP request packet.

This includes,
DHCP Server's IP address so that other can cool down their IP address so client gets from who it wants.
Client's hardware address so that client hardware->IP address mapping can be done.
Destination address is All Fs, so that all hosts receive the notification.

4) Acknowledgement.

I am following TCP/IP foundations by Black and I'm confused how will the client know that the acknowledgement came for it?

What is the general architecture of a network that comprises of Web Application Firewall(F5), Firewall, VPN, reverse proxy(nginx)?

I am new to this field and I am wondering what the architecture in general looks like? And where can I learn more about this? Any courses or certification exams that I can do to boost my network architecture skills?

I've read these stuffs:
We've tried mobile data and different ISPs and the problem seems to persist.


https://maulwuff.de/research/ssl-debugging.html



https://serverfault.com/questions/872424/why-are-some-people-getting-a-connection-not-secure-page-when-accessing-my-serve

Would ssl pinning fix this issue of very few clients getting ssl error?

https://developers.wultra.com/components/ssl-pinning-android/1.3.x/documentation/

There is an option to install CA cert on android, but is it worth the hassle or is there something simpler and efficient?

I read the UNIX and LINUX system admin handbook about this topic but I'm not yet clear about it.
I'm wondering what's the real answer to this? And what information is it really telling?
I mean some say it's a kernel routing table and it confuses me.
Can you truly make me understand this stuff?

https://serverfault.com/questions/368567/why-is-it-3-way-handshake-and-not-more
https://serverfault.com/questions/369056/tcp-whats-the-purpose-of-the-third-step-of-3-way-handshake
https://networkengineering.stackexchange.com/questions/24068/why-do-we-need-a-3-way-handshake-why-not-just-2-way
https://gateoverflow.in/123902/three-handshake-handshake-problem-which-solved-handshake
I read all over the place but still can't find concrete answer on what problem does tcp 3 way handshake solves.
It must be designed in a clever approach.
PS how do I use this technique while building software architecture?

[Ok a brain teaser. I assure this is not a homework. I'm learning computer networks from scratch again as I love networking.]

Ok a brain teaser. I assure this is not a homework. I'm learning computer networks from scratch again as I love networking.


IP Layer:

Header Length=10
Total length=1000

TCP Layer:

Sequence Number=100
Header Length=5

Find the acknowledgement number.

I know the answer and I understand it a little bit, but I want to hear your perspectives on how you'd solve it.

Here's how the youtuber solved it:

Total size at IP layer=IP_header+TCP_header+TCP_data
or 1000 =10*4+5*4+TCP_data

=> TCP_data length=940

Sequence number of first byte=100 Thus sequence number of last byte=940+100-1=1039

So the next acknowledgement number is 1040.

How'd you solve it?

why'd it show 24 icmp?

This is from douglas comer's internetworking with tcp/ip. Since this is just for learning purposes, I expect an answer that helps me to simulate this in a local programming language/network and solve it programmatically or mathematically.

Here's the question:

Consider an ethernet that has one conventional host, H and 12 routers connected to it. Find a single(slightly illegal) frame carrying an IP packet that when sent by host H causes H to receive exactly 24 packets.

TBH I don't really understand the question.

The context is ICMP.

If a remote host connected to a server via VPN is not able to ping the server, how'd you determine if the issue is with VPN at "server side" or VPN at "client side"?

There are various network issues that are pretty common.
Things like "No route to host"....bla bla.
Is there a cookbook for troubleshooting these issues in Linux? The problem is it's not possible exactly to tell what's happening sometimes. So, having a cookbook reference (example bash cookbook by oreilly) would help imo. Troubleshooting guide kinda thing.

ok.

I'm just trying to be proactive and learn stuffs. I guess I don't need to. Maybe all I need is to chill for some time