How do I find out ip number (IP Address) of my Linux server using command line options?

You can use any one of the following command to find out your IP address, routing table, devices, tunnels, and much more.

[a] ip command : Display or configure ip network information.

[b] ifconfig command : Display or configure ip network information.

ip Command Example

To display ip address, enter:
$ ip addr show
Sample outputs:

1: lo:  mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0:  mtu 1500 qdisc mq state DOWN qlen 1000
    link/ether b8:ac:6f:65:31:e5 brd ff:ff:ff:ff:ff:ff
3: wlan0:  mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:21:6a:bf:2d:64 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.100/24 brd 192.168.1.255 scope global wlan0
    inet6 fe80::221:6aff:febf:2d64/64 scope link 
       valid_lft forever preferred_lft forever
4: virbr0:  mtu 1500 qdisc noqueue state UNKNOWN 
    link/ether c2:86:1d:f6:17:a1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
    inet6 fe80::c086:1dff:fef6:17a1/64 scope link 
       valid_lft forever preferred_lft forever
6: pan0:  mtu 1500 qdisc noop state DOWN 
    link/ether fe:84:69:82:05:fb brd ff:ff:ff:ff:ff:ff
8: ppp0:  mtu 1496 qdisc pfifo_fast state UNKNOWN qlen 3
    link/ppp 
    inet 10.1.3.180 peer 10.0.31.18/32 scope global ppp0

To see eth0 or wlan0 interface ip info, enter:
$ ip addr show eth0
OR
$ ip addr show wlan0
To see current routing table, enter:
$ ip route show
Sample outputs:

10.0.31.18 dev ppp0  proto kernel  scope link  src 10.1.3.180 
38.96.196.94 via 192.168.1.2 dev wlan0  src 192.168.1.100 
192.168.1.0/24 dev wlan0  proto kernel  scope link  src 192.168.1.100  metric 2 
192.168.122.0/24 dev virbr0  proto kernel  scope link  src 192.168.122.1 
169.254.0.0/16 dev wlan0  scope link  metric 1000 
10.0.0.0/8 dev ppp0  scope link 
default via 192.168.1.2 dev wlan0  proto static 

To see your dns address, enter:
$ cat /etc/resolv.conf
Sample outputs:

domain nixcraft.net.in
search nixcraft.net.in
nameserver 127.0.0.1
nameserver 192.168.1.2
nameserver 10.1.2.30

To see network stats, enter:
$ netstat -i
Sample outputs:

Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0       1500 0         0      0      0 0             0      0      0      0 BMU
lo        16436 0        34      0      0 0            34      0      0      0 LRU
ppp0       1496 0      1734      0      0 0          2348      0      0      0 MOPRU
virbr0     1500 0         0      0      0 0             6      0      0      0 BMRU
wlan0      1500 0   2663556      0      0 0       2393688      0      0      0 BMRU

To see detailed stats, enter:
$ netstat -s

Ip:
    2665087 total packets received
    0 forwarded
    0 incoming packets discarded
    2664956 incoming packets delivered
    2395808 requests sent out
    5 dropped because of missing route
    189 reassemblies required
    91 packets reassembled ok
Icmp:
    84 ICMP messages received
    28 input ICMP message failed.
    ICMP input histogram:
        destination unreachable: 22
        timeout in transit: 60
        echo replies: 2
    375 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
        destination unreachable: 371
        echo request: 4
IcmpMsg:
        InType0: 2
        InType3: 22
        InType11: 60
        OutType3: 371
        OutType8: 4
Tcp:
    20610 active connections openings
    31585 passive connection openings
    8024 failed connection attempts
    1251 connection resets received
    5 connections established
    2581197 segments received
    2297196 segments send out
    63443 segments retransmited
    14 bad segments received.
    30535 resets sent
Udp:
    80731 packets received
    351 packets to unknown port received.
    1 packet receive errors
    31985 packets sent
UdpLite:
TcpExt:
    15213 invalid SYN cookies received
    159 resets received for embryonic SYN_RECV sockets
    622 packets pruned from receive queue because of socket buffer overrun
    7 packets dropped from out-of-order queue because of socket buffer overrun
    10 ICMP packets dropped because they were out-of-window
    15991 TCP sockets finished time wait in fast timer
    69 packets rejects in established connections because of timestamp
    31774 delayed acks sent
    7 delayed acks further delayed because of locked socket
    Quick ack mode was activated 55974 times
    3 packets directly queued to recvmsg prequeue.
    3 bytes directly received in process context from prequeue
    1172856 packet headers predicted
    152280 acknowledgments not containing data payload received
    19065 predicted acknowledgments
    847 times recovered from packet loss by selective acknowledgements
    Detected reordering 2 times using SACK
    Detected reordering 2 times using time stamp
    1 congestion windows fully recovered without slow start
    3 congestion windows partially recovered using Hoe heuristic
    420 congestion windows recovered without slow start by DSACK
    3090 congestion windows recovered without slow start after partial ack
    1097 TCP data loss events
    TCPLostRetransmit: 54
    1 timeouts after reno fast retransmit
    1302 timeouts after SACK recovery
    416 timeouts in loss state
    1264 fast retransmits
    28 forward retransmits
    2097 retransmits in slow start
    29729 other TCP timeouts
    217 SACK retransmits failed
    7416 packets collapsed in receive queue due to low socket buffer
    85705 DSACKs sent for old packets
    8290 DSACKs sent for out of order packets
    2556 DSACKs received
    17 DSACKs for out of order packets received
    9960 connections reset due to unexpected data
    328 connections reset due to early user close
    8346 connections aborted due to timeout
    TCPDSACKIgnoredOld: 1498
    TCPDSACKIgnoredNoUndo: 412
    TCPSpuriousRTOs: 27
    TCPSackShiftFallback: 5906
IpExt:
    InNoRoutes: 1
    InOctets: 1851631423
    OutOctets: 225338929

To see TCP / UDP network and socket information, use the ss command as follows:
# ss -s
# ss -l
# ss -t -a
# ss -u -a

ifconfig Command Example

Simply type the following command:
# ifconfig
OR
# ifconfig eth0
# ifconfig wlan0
Sample outputs:

wlan0     Link encap:Ethernet  HWaddr 00:21:6a:bf:2d:64  
          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::221:6aff:febf:2d64/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2664664 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2394780 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1888550078 (1.8 GB)  TX bytes:301911646 (301.9 MB)