CEN610S Core Engineering Networks - IPv4 Addressing and Prefixes

Flashcards covering IPv4 addressing, prefixes, subnet masks, and related concepts from the lecture notes.

What is the basis of IP networks?

The use of routing tables to decide how to route IP packets.

What are the two key elements IPv4 is built around?

(1) IP address; (2) Subnet mask.

How are IPv4 addresses written?

In dotted quad notation (A.B.C.D), with 8 bits per octet.

How many bits are in an IPv4 address and how does that compare to IPv6?

IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses.

What is an IP prefix?

A block of addresses sharing the same top L bits; the number of addresses is 2^(32−L) for hosts/routers.

What does the notation address/length mean?

It identifies a prefix where 'length' is the number of leading bits in the network portion; e.g., 128.13.0.0/16 covers 128.13.0.0 through 128.13.255.255.

What does a more specific (longer) prefix imply?

Fewer addresses in the prefix; a more precise route.

What does a less specific (shorter) prefix imply?

More addresses in the prefix; a broader network.

What were IP address classes (historical) and their network/host portions?

Class A: 8-bit network, 24-bit host; Class B: 16-bit network, 16-bit host; Class C: 24-bit network, 8-bit host.

What are public IP addresses?

Globally routable addresses on the Internet that must be allocated and are typically scarce.

What are private IP address ranges?

10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; used inside private networks and require NAT to reach the Internet.

What is NAT?

Network Address Translation; allows private networks to access the Internet using public addresses.

How are public IP addresses allocated?

IANA delegates to RIRs (e.g., ARIN, APNIC, RIPE, LACNIC, AfriNIC), which delegate to ISPs/enterprises, who assign to customers (often via DHCP).

What is the default subnet mask for a Class B address?

255.255.0.0 (equivalently /16).

What is the purpose of a subnet mask in IP communications?

To determine whether the destination host is on the local network by comparing network IDs.

What is the process called when computing whether a destination is local by combining an address with the subnet mask?

ANDing (bitwise AND of the IP address with the subnet mask).

What does it mean if the two ANDed results match?

The destination is on the local network; the host can communicate directly without a router.

What does it mean if the two ANDed results do not match?

The destination is on a different subnet; a router must be used to reach it.