🌐 NETWORKING

# Walk entire MIB tree (v2c)
snmpwalk -v2c -c public 192.168.1.1

# Walk specific OID subtree
snmpwalk -v2c -c public 192.168.1.1 system
snmpwalk -v2c -c public 192.168.1.1 interfaces
snmpwalk -v2c -c public 192.168.1.1 1.3.6.1.2.1.1

# Walk with SNMPv3
snmpwalk -v3 -l authPriv -u admin -a SHA -A authpass -x AES -X privpass 192.168.1.1

# Get system description
snmpget -v2c -c public 192.168.1.1 sysDescr.0

# Get system uptime
snmpget -v2c -c public 192.168.1.1 sysUpTime.0

# Get hostname
snmpget -v2c -c public 192.168.1.1 sysName.0

# Get interface speed by OID
snmpget -v2c -c public 192.168.1.1 1.3.6.1.2.1.2.2.1.5.1

# Set a value (requires write community)
snmpset -v2c -c private 192.168.1.1 sysName.0 s "NewHostname"

# Bulk walk (faster than snmpwalk)
snmpbulkwalk -v2c -c public 192.168.1.1 interfaces

# Test SNMP connectivity
snmpstatus -v2c -c public 192.168.1.1

# Translate OID to human-readable
snmptranslate 1.3.6.1.2.1.1.1.0
snmptranslate -On sysDescr.0      # reverse: name to OID

# Ping & reachability
ping -c 4 8.8.8.8               # 4 ICMP echo requests
ping -i 0.2 -c 10 192.168.1.1  # fast ping every 0.2s
ping6 ::1                       # ping IPv6 loopback

# Traceroute
traceroute 8.8.8.8             # trace path to host
traceroute -n 8.8.8.8          # no DNS resolution (faster)
mtr 8.8.8.8                    # live traceroute + ping combined
mtr --report 8.8.8.8          # generate report and exit

# DNS diagnostics
dig google.com                 # full DNS query
dig google.com A              # A record only
dig google.com MX             # mail records
dig google.com NS             # nameserver records
dig +short google.com        # short answer only
dig @8.8.8.8 google.com      # query specific DNS server
nslookup google.com           # simple DNS lookup

# Port & connection checking
nc -zv 192.168.1.1 80         # test if port is open (netcat)
nc -zv 192.168.1.1 20-25     # test port range
telnet 192.168.1.1 80         # manual port test
curl -v https://example.com   # full HTTP request with headers

# Packet capture
tcpdump -i eth0               # capture on interface
tcpdump -i eth0 port 80      # filter by port
tcpdump -i eth0 host 8.8.8.8 # filter by host
tcpdump -w capture.pcap      # save to file (open in Wireshark)
tcpdump -r capture.pcap      # read saved capture

ufw status                    # show firewall status
ufw enable                    # enable firewall
ufw disable                   # disable firewall
ufw allow 22                  # allow SSH
ufw allow 80/tcp             # allow HTTP
ufw allow from 192.168.1.0/24 # allow entire subnet
ufw deny 23                   # block Telnet
ufw delete allow 80          # remove a rule
ufw reset                     # reset all rules

iptables -L -n -v            # list all rules verbose
iptables -A INPUT -p tcp --dport 22 -j ACCEPT   # allow SSH in
iptables -A INPUT -p tcp --dport 80 -j ACCEPT   # allow HTTP in
iptables -A INPUT -j DROP   # drop all other inbound
iptables -D INPUT 1         # delete rule 1 from INPUT chain
iptables -F                  # flush (clear) all rules
iptables-save                 # save current rules
iptables-restore              # restore saved rules