Core Java Understanding.

There are three main things in Java.

1. The JVM: This is the Java Virtual Machine. Now the deal is that this is an abstract concept.
2. The JRE: This is the actual implementation of the JVM. You thus have a JRE for Windows, Linux, Mac etc.
3. The JDK: This is the JRE + other stuff needed to program in Java. For instance, there is the Java Complier, the Debugger, the Profiler etc.

How to look at a network / Do design decisions.

Look at a network along 3 vectors:

1. Address
2. Route
3. Queue

Address: Each protocol / layer brings in its own address space. For instance; VLAN’s bring VLAN ID’s. Its own address space.
Route: Each protocol decides how its going to route packets. For instance STP decides its route. VLAN implicitly defines a route by constraining the broadcast domain.
Queue / QoS: Each protocol / layer may brings in its own queueing space. For instance, HSRP brings a link up / down based on certain conditions. This link is a queue. VLAN does not have a queue.

So make a spreadsheet. X axis is Address, Route and Queue. Y axis is like a drawer. Each drawer has a bunch of protocols and each drawer has a category for instance a protocol would be STP and the category would be L2 loop prevention.