MonthMarch 2021

Blog 04 – OSI Model

Intro to the OSI model and Top-Down network design.
The OSI model depicts the layers that make up a network with every layer depending on the ones below it. For example: the Application layer depends on the Presentation layer which depends on the Session layer and so forth.

Top-Down network design is an agile methodology used in the construction of a network. This process defines what the network must be capable by looking at the business requirements of an organisation. This ensures that every layer meets the needs of the one above it.

     Top-Down network design steps
1. Analyse requirements
2. Develop logical design
3. Develop physical design
4. Test, optimize and document design
5. Implement and test network
6. Monitor and optimize network performance
Repeat as needed

     OSI Model
7. Application layer
6.  Presentation layer
5.  Session layer
4.  Transport layer
3.  Network layer
2.  Data link layer
1.  Physical layer

Blog 03 – Even More Subnetting

Ok so…. we’re still doing subnetting and Lars isn’t really covering anything new…
Basically all we’re doing right now is activities to practice. Kinda feels like maths homework….

I’m still trying to wrap my head around some of the finer points but as far as I can tell it’s mostly making sense.

Blog 02 – More Subnetting

We’ve continued to delve deeper into subnetting and the maths behind it. Lars keeps explaining it with different examples but I’m just getting more confused by how he does it. I feel like he is not properly explaining the cause and effect of what he is doing.
I would feel like an idiot, but I’m not the only one having problems with this.

What been helping my understanding the most was an online calculator I found. By using it I could clearly see how different parts of the equation affect each other, and after some fiddling I was starting to figure out why each part was being affected in the way it was.

Blog 01 – Subnetting

Subnetting allows you to partition a physical network into multiple smaller sub-networks (subnets). With this, it is possible to increase or decrease the number of IP addresses available on a single net address.

The basic structure for an IPv4 binary address with a 24 bit subnet mask is:
nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh
n = network part of the address
h = host part of the address
s = subnet part of the address
If we were to switch the first ‘h’ for an ‘s’ we would be able to use that bit as a network address. This would give us more net addresses to use but would reduce the number of IP addresses available for each address.