Week 6 Preview: Subnetting and VLSM - savannahc502/SavC-TechJournal-NET215 GitHub Wiki
Information on this page may be paraphrased or copied from Champlain College materials. Avoid coping as you may be committing plagiarism. This is for note-taking and academic purposes only.
Subnetting Intro Video
- Assignment of network addresses are done by the Internet Assigned Numbers Authority (IANA)
- For example, Champlain College uses 216.93.144.0/20 --> Champlain IPs all start with the same 20 bits
- Organizations will often break up their host bits in order to create multiple networks - this is called VLSM
- All 0's in the host ID refer to the network itself and cannot be assigned to a host
- All 1's in the host ID is the broadcast
- All 0's or 1's in a subnet ID is okay
- All of the systems must use the first 20 bits, but the last 12 can be broken up however you want.
Private and Reserved IP Ranges
Private Ranges not routable on the internet:
- 10.0.0.0/18
- 172.16.0.0/12
- 192.168.0.0/16
Reserved Ranges:
- 127.0.0.0/8 --> Loopback
- 169.254.0.0/16 --> Link-Local Host Only
- 224.0.0.0/4 --> Multicast
Classful Addressing Video
Some History:
- IPv4 originally designed to have 5 default subnet masks or "classes" ^
- Had prefixes in the beginning of the address to indicate the class type
- This was very limiting, thus CIDR was introduced to address the limitations of classful addressing
Creating Subnets with VLSM Video
A Technique for figuring out subnet's CIDR:
- Whenever you want to divide a network in half, move the netmask to the right by one.
- Each resulting subnet will have have half as many possible nodes
- Keep dividing in half until you reach the desired number
Week 6 Preview Quiz Notes
Had to fill out the entire table below using the following information:
- Main Office: 750 hosts
- Research Lab: 400 hosts
- Manufacturing: 400 hosts
- Sales Office: 200 hosts
- Telecommuter VPN: 200 hosts
| Location | Network Address | Subnet Mask | CIDR | First Usable IP | Last Usable IP |
|---|---|---|---|---|---|
| Main Office | 192.168.0.0 | 255.255.252.0 | /22 | 192.168.0.1 | 192.168.3.254 |
| Research Lab | 192.168.4.0 | 255.255.254.0 | /23 | 192.168.4.1 | 192.168.5.254 |
| Manufacturing | 192.168.6.0 | 255.255.254.0 | /23 | 192.168.6.1 | 192.168.7.254 |
| Sales Office | 192.168.8.0 | 255.255.255.0 | /24 | 192.168.8.1 | 192.168.8.254 |
| Telecommuter VPN | 192.168.9.0 | 255.255.255.0 | /24 | 192.168.9.1 | 192.168.9.254 |
Had to fill out the entire table below using the following information:
- Foster Hall: 225 hosts
- Skiff 100: 25 hosts
- Joyce 310: 25 hosts
| Location | Network Address | CIDR | First Usable IP | Last Usable IP |
|---|---|---|---|---|
| Foster Hall | 216.93.144.0 | /24 | 216.93.144.1 | 216.93.144.254 |
| Skiff | 216.93.145.0 | /27 | 216.93.145.1 | 216.93.145.30 |
| Joyce | 216.93.145.32 | /27 | 216.93.145.33 | 216.93.145.62 |
Helpful Subnetting Links
- IP Calculator
- VLSM Calculator
- CIDR Conversion
- Available Hosts per Subnet
- Lab 7-1 Subnetting Chart from NET-150
- NET-150 GitHub Notes IP Addressing
- NET-150 GitHub Notes Basic Subnetting
How to Implement VLSM Subnetting:
How to Implement VLSM Subnetting:
- In a routing table, arrange the networks from largest to smallest number of hosts needed.
- Subnet the largest LAN first using the closest number of hosts a CIDR provides (for example, if you need 59 hosts you will use CIDR /26 because it provides 64 hosts in 4 subnets).
- Build the largest LAN's information including network address, subnet mask, CIDR, first and last usable hosts, and broadcast ID.
- Assign the CIDR to the other networks and build up the network addresses. Remember that each subnet has 256 addresses, from .0-.255
- This means you'll often see the last usable host end in .254, unless your CIDR delegates less than 256 addresses.
- The first address is the network address, and the last is the broadcast address.
- Don't forget to include the networks between routers, as they need their own IP addresses.