Interview_IP address

📌 IP address

✅ What is IP address?

- address for each device connected to network

✅ Two parts of IP address?

- network part ➕ host part
- network part가 같다면 같은 네트워트 ➡️ switch, bridge, hub
- network part가 같다면 다른 네트워트 ➡️ router
- each device has unique host address

✅ If devices are on different network, how does it communicate?

- through router
- router creates broadcast domain

✅ What is the difference between IPv4 and IPv6?

- IPv4: 32bit binary(total 2^32)/ 8 * 4parts/ in decimal, seperate with .
- IPv6: 128bit binary(total 2^128)/16 * 8parts/ in hexadecimal, seperate with :

✅ How are the classes of IP address?

- class A: network 8 + host 24, start with 0
- class B: network 16 + host 16, start with 10
- class C: network 24 + host 8, start with 110
- class D, E

✅ What is CIDR?

- Classless Interdomain Routing
- devide network part, host part of IP address more flexibily than class

📌 MTU

✅ What is MTU?

- Maximum Transmission Unit
- Max data that can be sent
- differs on protocol, link
- ⭐️ fragmentation, reassembly

✅ What is in MTU header?

- ID
- flag
- offset

📌 Subnet, Subnet Mask

✅ What is Subnet?

- small isolated part of network

✅ Why do we have to make network into smaller subnets?

- If we use IP address as recieved, broadcast domain is too big
- If broadcast domain is too big, more network load

✅ What is subnet mask?

- use subnet mask to distinguish IP address into network part and host part
- 1: network part, 0: host part
- example: /20 means first 20 binary numbers are network part

✅ Why do we use subnet mask?

- 1. Make network into smaller subnets
- 2. Save IP address

✅ What is broadcasting?

- one way to trasnmit data from node to node
- one node to all nodes
- exmaple: ARP, DHCP

- 👎🏻 lot of network traffic, as message is sent to every node in network
- 👎🏻 less secure

- 🆚 unicast: point to point
- 🆚 multicast: multiple point to point

✅ If subnet mask is /24, how many hosts can be on network?

- 32-24 = 8
- 2^8-2
- 000000: for network address
- 111111: for broadcast address
- others can be used for device IP address, gateway

📌 Routing

✅ What is a router?

- route network traffic
- create broadcast domain
- OSI layer 3
- use IP address to route data
- has routing table

✅ What is broadcast domain?

- when not knowing IP address, send to all device on broadcast domain "who"?

✅ What is routing?

- route network traffic among different network
- look at IP address network part
- If network part is differnet, has to go through router

✅ What is gateway?

- to access totally dissimilar network
- access control

📌 Routing Protocol

✅ What is routing protocol?

- protocol to decide how to route data packet from src to dest
- find best route
- update routing table

✅ Distance Vector Routing Protocol
- select path on hop counts
- RIP
- hop count: how many router between src and dest?

✅ Link State Vector Protocol
- every node constructs a map of the connectivity of network in form of graph
- which node is connected to which
- more about internetwork
- OSPF

✅ Advanced Distance Vector Routing Protocol
- hybrid routing protocol
- EIGRP

⭐️ RIP
- Routing Information Protocol
- maximum hop: 15, not suitable for big networks

⭐️ OSPF
- Open Shortest Path First
- caculate shortest path spanning tree

⭐️ IGRP - Interior Gateway Protocol
- more than 15 hops, maximum hop: 255 - suitable for larger networks
⭐️ EGP
- Exterior Gateway Protocol

⭐️ EIGRP
- Enhanced Interior Gateway Routing Protocol
⭐️ BGP
- Border Gateway Protocol
- replaced EGP

✅ What is DHCP?

- Dynamic Host Configuration Protocol
- DHCP server automatically assigns IP address when new host joins a network
- client-server based
- message ➡️ request ➡️ response with IP address
- when host sends DHCP message, use broadcasting

✅ How is IP address assigned?

- Static Assignment: manually assign static IP
👍🏻 can predict network
👍🏻 address is static, doesnt change
👎🏻 difficult to manage, address collision
🛠️ printer, server, important network devies
- Dynamic Assignment: automatically assign dynamic IP addressby DHCP
- only valid for limited time, need revalidation
👍🏻 automatic 👍🏻 easy to manage, prevent address collision 👎🏻 IP address can change dynamically 🛠️

📌 NAT, Private IP, Public IP

✅ What is private IP and public IP?

- Private IP: IP used in private network
- cannot be accessed from outside
- cannot access Internet
- Public IP: IP to access Internet

✅ What is NAT?

- Network Address Translation
- private IP ➡️ NAT ➡️ public IP
- host in private network request with private IP, port
- NAT translate into public IP, assign port
- update NAT translation table
- web server reply arrive to public IP address
- NAT translate again to private IP, send to host

✅ What are the benefits of using NAT?

- 👍🏻 security, private IP access impossible
- 👍🏻 save IP address(several private devices use one public IP address)
- 👍🏻 devices in private network can access Internet

🆚 Mac address

IP address 🆚 Mac address?

✔️ Mac address
- physical unique identifier on NIC card
- hardware address that is physically embedded into NIC
- OSI layer 2, switch, bridge, collision domain
- 48bit number

✔️ IP address
- logical identifier assigned to device when joining network
- OSI layer 3, router
- IPv4, IPv6

✔️ ARP
- IP address ➡️ map to Mac address

📌 ICMP

✅ What is ICMP?

- Internet Control Message Protocol
- part of Internet Protocol
- IP does not have error reporting function
- ICMP provide error handling in network layer of OSI layer
- 1. Error Handling: if data packet did not arrive, report
- 2. Network assessment: ping
- ping: echo request message - check packet loss or delay
- (check if there is a connection between two devies)
- (measure the time to reach dest)
- traceroute: know the route between two devices