IP address

CIDR

• 192.168.0.0/24
• 192.168.0.0 -> 192.168.0.255
• 2^(32-X) = 2^(32-24) = 2^8 = 256

Private IP

• 192.168.0.0/16
• 172.16.0.0/12
• 10.0.0.0/8

Subnet

• 192.168.0.0/16
• Subnet = 192.168.0.0

Broadcast

• 192.168.0.0/16
• Broadcast = 192.168.255.255
• Messages received by machines 192.168.0.0 -> 192.168.255.254

Gateway

• 192.168.0.0/16
• Gateway (usely) = 192.168.0.1
• Network node equipped for interfacing with another network
• When a machine want to speak outside, it send data to the gateway

Terminology

• 192.168.0.0/16 => Subnet
• 192.168.0.0 => SubnetId
• /16 => BitMask
• 192.168.0.1 => Gateway
• 192.168.255.255 => Broadcast

NAT

• Network address translation
• Remapping one IP address into another

Load Balancer

Distributes workloads across multiple computing resources

Algorithm

• Round robin
• Weighted round robin
• Least connections
• Least response time
• Least Sessions

Persistance

• Cookie
• Source address
• SSL
• SIP

HTTPS

Monitoring

• active vs passive
• ping
• tcp / udp
• HTTP(s) / FTP / IMAP / etc...

Firewall

Network security system that controls the incoming and outgoing network traffic

How does it work

• List of rules
• One rule contains:
  • source: IP / range
  • destination: IP / range
  • service: protocol + port
  • policy: allow | drop
• First match = First win

Service == ?

• list of ports
• protocol
  • tcp
  • udp
  • icmp

Source or destination

Service FTP

active

passive

Best Practice

• Deny all by default
• Last rule is equals to:
  • source: ANY
  • destination: ANY
  • service: ANY
  • policy: drop

VLAN

• Isolate multiple subnet inside switch/router
• Grouping host with a common set of requirements
• Split private network and public network

Architecture

SSH Forwarding

laptop$ apt-get install squid

laptop$ ssh -R 3128:localhost:3128 user@back_server

user@back_server$ export http_proxy=http://127.0.0.1:3128/

user@back_server$ apt-get update

SDN

Software Defined Network

Concept

• Directly programmable
• Centrally managed
• Programmatically configured
• Open Standards-based / Vendor neutral

Control plane

• Makes decisions about where traffic is sent
• include the system configuration, management, and exchange of routing table information
• routers exchanges the topology information with other routers

Data plane

• Forwards traffic to the next hop along the path to the selected destination network according to control plane logic