netpractice

internet protocol or: how i learned to stop worrying and love the router

references korean translation comming soon (ish)

Things to remember

IPv4

• 0 ~ 255 * 4 = 4 bytes = 32 bits

Private IPv4 addresses

• can be only used within the same network
• 10.0.0.0/8
• 172.16.0.0/12
• 192.168.0.0./16

Subnet Masks

• apply AND ops to get the network address
• CIDR notation = /{number of 1s in binary}
• first and last of an address range is reserved
  • first: network ID address
  • last: broadcast address

Interface

• network is like shouting numbers at each other
• so individual's address must not overlap with others
• interfaces will decide to only listen to numbers within their range
• that range is the subnet mask

Switch

• distributes packets to local network
• can be ignored in the subject, since it doesn't do much

Router

• connects multiple different network addresses
• so its addresses (and their ranges) must not overlap

Routing table

• if a packet's destination address is not within local network, the router won't know where to send
• but it could 'toss' the packet to another router, so that router may know where to send it
• if one of the destination in routing table match with packet's, the router will send it to the 'next hop'
• if 'next hop' knows the destination, it will send it to the destination, if not, hop again and again...
• default == 0.0.0.0/0, since every ip address would match

Levels

Basics: subnet mask, network address, and ip range

Intermidiate: routing, routing table, network address overlap

Advanced: multiple different CIDR