How To List Connected IPs To Server?
List Kernel IP Routing
List Network Interface Transactions
Check IPv4 & IPv6 Information
Usage of netstat Command
netstat is a command-line utility to list network connections, routing tables, interface statistics multicast memberships and masquerade connections.
# List all ports and IPs (tcp and upd)
netstat -a | more
Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:sunrpc *:* LISTEN tcp 0 52 192.168.0.2:ssh 192.168.0.1:egs ESTABLISHED tcp 1 0 192.168.0.2:59292 www.gov.com:http CLOSE_WAIT tcp 0 0 localhost:smtp *:* LISTEN tcp 0 0 *:59482 *:* LISTEN udp 0 0 *:35036 *:* udp 0 0 *:npmp-local *:* Active UNIX domain sockets (servers and established) Proto RefCnt Flags Type State I-Node Path unix 2 [ ACC ] STREAM LISTENING 16972 /tmp/orbit-root/linc-76b-0-6fa08790553d6 unix 2 [ ACC ] STREAM LISTENING 17149 /tmp/orbit-root/linc-794-0-7058d584166d2
# List Only IPs
netstat -tn 2>/dev/null | grep :80 | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr | head
- Here -t is for tcp connections
- 2>/dev/null redirects all unwanted output to /dev/null
- grep :80 displays results only for IPs connected on port 80
- awk '{print $5}' displays fifth column only
- cut -d : -f1 is used to extract only IPs excluding port with delimeter ":"
- sort command sort the result
- uniq command groups the result
- sort -nr again sort it in reverse order
- head will display top 10 results
# Display kernel IP routing
netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0 link-local * 255.255.0.0 U 0 0 0 eth0 default 192.168.0.1 0.0.0.0 UG 0 0 0 eth0
# List Network Interface Transactions
netstat -i Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth0 1500 0 4459 0 0 0 4057 0 0 0 BMRU lo 16436 0 8 0 0 0 8 0 0 0 LRU
# Check IPv4 & IPv6 Information
netstat -g IPv6/IPv4 Group Memberships Interface RefCnt Group --------------- ------ --------------------- lo 1 all-systems.mcast.net eth0 1 224.0.0.251 eth0 1 all-systems.mcast.net lo 1 ff02::1 eth0 1 ff02::202 eth0 1 ff02::1:ffb4:da21 eth0 1 ff02::1
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