Networking
December 23, 2020 ยท View on GitHub
General
Q: What is the benefit of a protocol like QUIC?
Q: Why would you potentially want to use UDP for a long-distance VPN connection (non commercial)?
Q: What protocol is usually used within corporate networks?
Q: What are some of the TCP congestion protocols?
Q: What is IP fragmentation?
Q: Explain how ping works?
IP Addressing
Q? How many usable addresses in a /24?
A: 254 (including gateway address)
Q: How many usable addresses in a /31?
A: Technically 0, but in practice 2
Q: How many usable addresses in a /30? A: 2
Q: How large is a /16?
A: = 65536
Q: What is RFC-1918?
A:
- Address Allocation for Private Internets
- 10/8, 172.16/12, 192.168/16 prefixes are assigned here
Q: What is the subnet mask of 10.2.1.2/22? A:
- 255.255.252.0
- See IPv4 subnetting cheatsheet
OSI Model
Q:What is the OSI model?
A:
- Physical
- Data
- Network
- Transport
- Session
- Presentation
- Application
Q: What is your favourite protocol in the OSI layer?
L1 Protocols
Q: Explain the L1 model?
*Q: What are some L1 protocols
Q: How do you troubleshoot a layer 1 issue with an ethernet jack?
Q: How do you troubleshoot a flapping link between 2 routers?
L2 Protocols
Q: Describe the Ethernet Protocol?
Q: What is ARP?
Q: What is the purpose of the broadcast address in a network?
L3 Protocols
IPv4
Q: Describe an IPv4 packet
Q: What is the purpose of the ECN field?
Q: What are some of the options that can be set in an IPv4 field?
*Q: What are examples of IP protocols?
A:
Q: Describe IP-in-IP
IPv6
- Describe an IPv6 packet
- What are some benefits of IPv6
ICMP
- Describe how traceroute works
- Describe how ping works
- Describe how tcptraceroute works
L4 Protocols
TCP
- What are the 6 TCP flags
L7 Protocols
Q: Name some L7 protocols?
A:
- DNS
- HTTP/ HTTPS/ HTTP2
- QUIC
- NTP
- SNMP
- SSH
Loadbalancing
-
What's the difference between a L2, L4, L7 load-balancer
-
What are the various load-balancing methods? ** Round Robin ** Weighted Round Robin ** Least Connections ** Weighted least connections ** Fixed Weighting ** Hash (L7) ** SRC IP Hash ** Response time ** Power of Two Random Choices
Routing Protocols
BGP
Q: What the 6 BGP session states?
A:
- Idle
- Connect
- Active
- OpenSent
- OpenConfirm
- Established
Q: What port/ protocol does BGP run on?
A: TCP/179
Q: Explain the difference between eBGP and iBGP?
A:
- eBGP is used for communication between different autonomous systems
- Reference
Q: What is the smallest prefix size you can publically announce?
A: Reliably /24
Q: What is a BGP community?
A:
Q: What is the administrative distance BGP uses for iBGP and eBGP?
A:
- iBGP 200
- eBGP 20
Q: What is the difference between a hard reset and soft reset? A:
Q: What are the different BGP message types?
A:
Q: What are the BGP path attributes?
A:
Q: What is an AS?
Q: What is a route reflector?
A:
Q: What is the BGP path selection criteria?
Q: What is the purpose of route dampening?
OSPF
Q: What is a OSPF?
Q: What are the steps to create router adjacency?
Q: What is a LSA? Q: What is a LSU?
Q: What is a LSR?
Q: What is an OSPF backbone area?
Q: What are the different neighbour states?
Q: What are the different OSPF network types?
Q: What is the default link cost?
Q: Explain stubby areas and non-so-stubby-area?
Q: What are the three types of authentication supported by OSPF?
Good Reads
- How do TCP Sockets work
- The inner workings of bind and listen on Linux
- How TCP backlog works in Linux
- SYN Packet handling in the wild