Speaker: Sean Whitesell @codewithseanw

For more, see the table of contents

Home networking

• Lots of devices at home
• Some devices require connectivity to phone home or won’t operate
• Home devices connect to router
• LAN – router <–> home devices
• WAN – router <–> internet
• Local devices not having IP exposed to world
• Packets – pieces of data – think of as train cars. Don’t put everyone in same car

DNS (Domain Name Service)

• Converts friendly name to address. Like calling a contact – you don’t know the phone number
• On Windows:
  • ipconfig /displaydns
  • ipconfig /flushdns
• A record – name to IP
• CNAME – alias – subdomain www.google.com points to google.com. Can route to elsewhere
• MX – mail exchange
• nslookup set type=NS (or MX or CNAME or AAAA for IPv6)
• nslookup url.com – can return multiple addresses so resiliency if goes down

Routing

• If mail a letter, look at zip code then street than address.
• Like a perimeter. Routing brings inside house
• IP v4 – 32 bits
• Subnet mask 255.255.255.0
• Class A – 0.0.0.0 – 127.255.255.255 – 128 networks, 16 million addresses
• Class B – 128.0.0.0 – 191.255.255.255 – 65K addresses
• Class C – 192.0.0.0 – 255.255.255.255 – 254 addresses
• RFC 1918 – non routable addresses
• CIDR (classless inter-domain routing) notation lets you waste less addresses – ex: 10/8

Network sizing

• If don’t pick enough have to move all devices
• 10.0.0.0/24 – CIDR says use first 24 bits – 256 addresses
• 10.0.0.0/23 – now use first 23 bits – 512 addressesCloud doesn’t let you do /30 because only 4 addresses and AWS/Azure use 5 addresses per subnet
• Subnets – like multiple rooms in a house. To partition things off

Network Address Translation

• 192.168.* means internal/non-routable address
• http://whatismyipaddress.com – shows public address
• Router keeps track of ports and which device to go to
• 65536 available ports. 0-1023 are reserved. Similarly browser tabs have ports to keep track of conversation

Common ports

• FTP – 20 and 21
• SSH – 22
• SMTP – 25
• DNS – 53
• Web and SSL/TLS, HTTP/HTTPs – 80 and 443
• SQL server – 1443

OSI (open system interconnect) model

• 7 – application – Azure App gateway, AWS ALB, Mginx
• 6 – presentation – SSL
• 5 – session
• 4 – transport – TCP (ack everything; very chatty) vs UDP (send and forget without confirmation), Azure LB, AWS NLB
• 3- network – IP
• 2 – data
• 1 – physical

North-South East-West Security Model

• DMZ
• App Server Layer
• Database Layer

Route table

• Control and enforce traffic
• Determine which traffic goes to firewall.
• Different rules for different subnets
• Private subnet has no internet access
• AWS has internet gateway – needed to get to internet

Cloud

• Load balancer – can be layer 4 or 7
• Network security groups – VM/EC2 level, stateful
• AWS NACL (network access control list_ stateless. One rule does not allow both directions

My take

This was a good overview. Some I knew. Some I used to know. Some was new. The end felt rushed. Regardless, I’m glad I attended.