IPv4 Subnetting Flashcards
What does the subnet mask do?
Identifies the network and host portion of an address
What are IP address ranges?
A: 1-126.x.x.x
B: 128-191.x.x.x
C: 192-223.x.x.x
What is TTL (time to live)?
The time for a ping request to expire
What are the private IP address ranges?
A: 10.x.x.x
B: 172.16-31.x.x
C: 192.168.x.x
What do private addresses use to resolve to a public IP address?
NAT
Network Address Translation
What Base does Binary use?
Base 2
What Base does Decimal use?
Base 10
What Base does Hexadecimal use?
Base 16
How do you convert decimal to binary?
Find the highest common denominator of a powers of 2 that goes into the decimal number. For an octet 2^0 - 2^7
When subnetting, how are each of the octet bits allocated?
Contiguously from left to right Think Network | Host mentality 11111111.11111111.11111111.00000000 Not: 11011111.11111111.11111101.00000000
How does the prefix length correspond with the subnet number?
/8 = 255.0.0.0 - Class A default /9 = 255.128.0.0 /10 = 255.192.0.0 /11 = 255.224.0.0 /12 = 255.240.0.0 /13 = 255.248.0.0 /14 = 255.252.0.0 /15 = 255.254.0.0 /16 = 255.255.0.0 Class B default
What are the valid host addresses within a subnet range? (when sacrificing host bits)
First host: subnet + 1
Last host: subnet - 2
What is the broadcast address for a subnet range? (when sacrificing host bits)
next subnet - 1
What are the two components of an IP address?
Network | Host
What are the components of a subnetted IP address?
Network | Subnet | Host
What determines if you can assign a host an IP address on a given subnetwork address?
You are not able to assign an IP address to a host if it is a subnetwork address with the host portion all 0s
How do you calculate number of hosts on a subnet?
32 - prefixlength = h
2^h - 2 = number of hosts available
How do you calculate the subnet of an IP address?
(Last network octet / Block size) * Block size
- remove remainder
- host octets will be 0 (everything to the right of network octet)
How do you calculate the subnets possible for a given network?
Subnets = 2^bits sacrificed from host
How do you calculate the subnet addresses for a given network?
Subnet is default 0.0.0.0 + Block size each time for number of subnets possible
How do you determine Block size for a subnet?
Last bit used in octet
In this case 2nd octet:
- 255.0.0 Block size = 2^0 = 1
- 252.0.0 Block size = 2^2 = 4
What does the summary address do?
Identifies which bits of an octet are in common
Simplifies the routing table
How do you summarise a network?
Determine common octets + common consecutive bits in changing octet
Take value of bits and change last network octet + prefixlength based on bits used
What is mask value?
Increments from left to right in a given octet based on bits used
What is a wildcard mask?
Inverted subnet mask
How do you determine the wildcard mask for a boundary that is not clean (/8, 16, /24)
Block size - 1
in mask value’s position
What is VLSM?
Variable Length Subnet Mask
How do you configure a VLSM?
List mask and subnets in order of most hosts required
After last subnet on a network increment by its block size again then start the next network
Repeat for point to point WAN links
What public address range is used for multicast?
224-239.x.x
How do you determine largest remaining block in VLSM?
32 - Address prefix length (h)
2^h total host addresses that can be allocated
Largest remaining = 2^h - VLSMs
