Cheatsheet: Linux Networking
- PDF Link: cheatsheet-networking-A4.pdf, Category: interview
- Blog URL: https://cheatsheet.dennyzhang.com/cheatsheet-networking-A4
- Related posts: CheatSheet: Linux File, CheatSheet: Linux Process, #denny-cheatsheets
1.1 Top 10 Networking Questions
| Num | Name | Summary |
|---|---|---|
| 1 | Difference between switch and router? | L2, L3 |
| 2 | What is a DNS amplification attack? | |
| 3 | Difference between L2 and L3 switch? | |
| 4 | What is TCP SYN scan? How it’s conducted? | |
| 5 | Which port ICMP is using? | Neither TCP or UDP. Link |
| 6 | Proxy server vs Loadbalancer. Proxy server vs Reverse proxy server | |
| 7 | Brief introduction about 802.1x | |
| 8 | List all methods which can stop one ip ssh to the server |
|
| 9 | Explain how iptable routing rules works |
1.2 Linux Networking
| Name | Comment |
|---|---|
| Examine network nic traffic | ethtool -S eth0 |
| Check system configuration | sysctl -a |
| Change linux machine hostname | /etc/sysconfig/network, /etc/hostname |
| Ports for well-known services | cat /etc/services |
| Reference | SSH CheatSheet, Tcpdump CheatSheet, CheatSheet: Curl & Wget |
| Reference | CheatSheet: Linux File, CheatSheet: Linux Process, CheatSheet: Linux Networking |
1.3 HTTP
| Name | Command |
|---|---|
| How HTTPS works | |
| Explain X509 certificates | |
| See HTTP request statistics | httpstat https://www.google.com (brew install httpstat) |
| Monitor HTTP URLs | SaaS: uptimerobot.com |
| Examine web page performance | SaaS: pingdom.com |
| Test webpage from different browsers | SaaS: www.browserling.com |
| Export local http service to Internet | SaaS: ngrok.com |
| Reference | CheatSheet: Curl & Wget, GitHub: free-for-dev |
1.4 TCP
| Name | Comment |
|---|---|
| List all listening tcp ports | netstat -tunlp |
| Port scan for a given host | sudo nmap -O 192.168.1.103, SaaS: viewdns.info/portscan |
| Add 97ms latency to eth0 | Link: tc, tc qdisc add dev eth0 root netem delay 97ms |
| Check tc status | tc -s qdisc |
| Remove tc rule | tc qdisc del dev eth0 root netem |
| Check network speed | SaaS: www.att.com/speedtest |
| Tcp manual | man 7 tcp |
| Disable ipv6 | Change systcl, by adding net.ipv6.conf.*.disableipv6 |
| Check for IPv6 support in the current kernel | /proc/net/if_inet6 |
| Reference | Tcpdump CheatSheet |
1.5 Route
| Name | Comment |
|---|---|
| List route rules | route -n, netstat -nr |
| Add default rule | route add default gw 10.0.0.1 netmask 255.255.255.0 dev eth0 |
| Add route rule | route add -net 0.0.0.0 gw 192.168.1.1 netmask 0.0.0.0 dev eth0 |
| Del route rule | route del -net 192.168.3.0 netmask 255.255.255.0 dev eth1 |
1.6 DNS
| Name | Comment |
|---|---|
| Check dns naming | sudo nslookup www.google.com |
| Print routing table | netstat -rn |
| List all the router hops | traceroute |
| DNS lookup utility | host www.google.com |
| DNS pin test | SaaS: viewdns.info |
| Websites To Register DNS | Link: Google Domain DNS, Link: GoDaddy, Link: Amazon Route 53 |
1.7 CDN
| Name | Command |
|---|---|
| CDN services | cloudflare, jsDelivr |
1.8 TCP sockets workflow
| Name | Comment |
|---|---|
| create a new anonymous socket | s = socket(<parameters>) |
| Bind tcp port to a socket | bind(s, <local IP:port>) |
| Create a socket to remote endpoint | connect(s, <remote IP:port>) |
| Create local socket and make it eligible to take requests | listen(s, ...) |
| Accept client requests | s2 = accept(s) |
| Read n bytes from a socket | n = read(s, buffer, n) |
| Write n bytes to a socket | n = write(s, buffer, n) |
| Close a socket | close(s) |
| Shutdown stdin and stdout/stderr for a socket | shutdown(s, <side>) |
| Read socket options | getsockopt(s, ..) |
| Change socket options | setsockopt(s, ..) |
1.9 More Resources
License: Code is licensed under MIT License.
https://github.com/trimstray/the-book-of-secret-knowledge
