The Network Layer, the Internet Protocol, and Routing

A quick introduction to studying the Network Layer. The layer of IP, routing, routers and more!

Network Layer
=======================
1. IP Internet Protocol
- IPv4, IPv6, ICMP,
- logical addressing (OSI Layer 3) ---as opposed to layer 2 physical addressing
- End-to-end addressing,

from(PC) --- Router --- ISP-Cloud --- Router --- to(PC) ---- and back again

2. Routers ---- Data Plane, Control Plane, QoS, SDN Software Defined Networking
3. Routing ---- host routing table and default gateway, router's routing table
4. Configuring a router

IP
===============
- IP packet header ------------ (IP header (transport header + Data))
- Connectionless ------------ no prior established connection at this layer
- Best Effort ------------ no reliability, no retransmission at this layer
- Media Independent ------------ works with fiber, copper, wireless, etc.
- IPv4 addressing
- network address ----------- 192.168.3.0 (first address in the network)
- broadcast address --------- 192.168.3.255 (last address in the network)
- host address ----------- 192.168.3.13
- netmask ----------- 255.255.255.0 (defines the network)
N N N H
- default gateway ----------- 192.168.3.1 (gateway is the router on the network)
- multicast address --------- 224.0.0.1 (used for sending to groups)

Routers
======================
Make forwarding decisions at Layer 3 ---------- Using Layer 3 header information (dst ip address)
Determine the Best Path ----------------------- Using the routing table
Forward data ----------------------- Move packet from input interface to output interface

Hosts Computers
======================
also make forwarding decisions at layer 3
also have routing tables ------------------- netstat -r
Use default gateway ------------------- for unknown networks (route table - 0.0.0.0 0.0.0.0 gateway)


Logical Addressing
==========================
192.168.44.211 -- IP address
255.255.255.0 -- subnet mask - /24, means there are 24 ones in the mask
N N N H - 11111111.11111111.11111111.00000000
==================
192 168 44 0 --- network
192 168 44 ? --- host
192 168 44 255 --- broadcast

Are the following addresses all on the same network? yes or no
192.168.44.111/24,
192.168.44.3/24,
192.168.44.252/24,
192.168.44.1/24

Are the following addresses all on the same network? yes or no
172.16.2.32/24,
172.16.2.6/24,
172.16.2.111/24,
172.16.20.167/24

[LucasFerreira-jykw]

Thank you for the info; i'm studying for ccna and also record videos about network and your content is helping me.

[kocin.sb_]

You are GOD Sir!!! Thank you for these amazing tutorials.

[ElsaFisaha-ku]

Thank you so much sir, its really helpful!

[professoreno]

Another great video... Keep them coming :-)

[sai]

Thank you sir, how to add route to hosts or computers from command prompt

[rainfordgrey]

Hi, I didn't know where to go for this so I'm going to comment sections regarding ISP routing. I had Xfinity in New Jersey. To a server in Quebec, Canada, I had gotten 40 ping. However I moved 20 minutes from there in a suburb extremely close nearby. Now, to the same server in Canada, I now have about 15 ping. I am so curious, but cannot figure out what could have been the problem there in terms of routing efficiency there. I've done traceroutes and the like, I don't know enough about the gateways to actually diagnose where the problem was. Was it a problem on my ISP's side? (also, on another server to Ashburn Virginia, at my old apartment I had gotten 60 ping with the same provider, now at my new house, I get about 8-10)