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Networking Commands

Network Interfaces and Configuration

  • Linux Commands:
  • ifconfig
    • Purpose: Display or configure network interfaces.
  • ip addr show or ip a
    • Purpose: Display IP addresses and property information for all interfaces.
  • Windows Command:
  • ipconfig
    • Purpose: Display all current TCP/IP network configuration values.

Routing and Network Traffic Management

  • IPv4 Forwarding:
  • sysctl -w net.ipv4.ip_forward=1
    • Purpose: Enable IPv4 forwarding temporarily.
  • Editing /etc/sysctl.conf to include net.ipv4.ip_forward=1
    • Purpose: Make IPv4 forwarding setting persistent across reboots.
  • sysctl -p
    • Purpose: Reload sysctl settings from /etc/sysctl.conf.

Firewall Configuration using iptables

  • Viewing Rules:
  • iptables -L
    • Purpose: List all active rules in the default filter table.
  • iptables -L -t <table>
    • Purpose: List rules in a specific table.
  • Adding Rules:
  • iptables -A <Chain> -s <IP> -j <Target>
    • Purpose: Append a rule to a chain for packets from a specific IP.
  • Deleting Rules:
  • iptables -D <ChainRule>
    • Purpose: Delete a specific rule from a chain.
  • Setting Default Policy:
  • iptables --policy INPUT DROP
    • Purpose: Set the default policy for the INPUT chain to DROP.
  • Deleting All Rules:
  • iptables -F
    • Purpose: Flush all rules, deleting them.
  • Specifying Protocols and Ports:
  • -p: Specify protocol (TCP/UDP).
  • --dport: Specify destination port.
  • --sport: Specify source port.
  • -s: Specify source IP address.
  • -d: Specify destination IP address.
  • Logging:
  • Purpose: Log packets that match a rule; viewed with journalctl.

Packet Sniffing and Analysis

  • tcpdump Usage:
  • tcpdump -i <interface>
    • Purpose: Capture packets on a specific network interface.
  • tcpdump -l -i <interface>
    • Purpose: Listens to the first 10 packets on that interface.
  • tcpdump -l -i <interface> | grep ICMP
    • Purpose: Show only the ping packets generated by ICMP.
  • tcpdump -n -l -i <interface> <protocol>
    • -Purpose
  • Filtering options provide more specific capture criteria, like protocol, source, and destination.

Service and Protocol Specific Configuration

  • SSH, TFTP, FTP Configuration:
  • Purpose: Instructions for configuring firewall rules to allow traffic for these services.
  • TCP and UDP:
  • Purpose: Discussion on handling traffic for these protocols in firewall rules.