UNIX Networking Command

UNIX Networking Commands

ping <remote machine> Sends an IP echo request to the <remote machine>

% ping burro.baylor.edu
burro.baylor.edu is alive

nslookup <machine name> Query name server to map names (e.g. burro.baylor.edu) to IP address and IP addresses to names (the reverse). Optionally, you can specify the name server you want to use. Under UNIX, the default name server for a machine can be found in the /etc/resolv.conf file. Under other OSs, it is in more obvious places such as the networking control panel.

% nslookup burro.baylor.edu
Server: ccis03.baylor.edu <= Name of queried name server
Address: 129.62.16.4 <= IP address of queried name server

Name: BURRO.baylor.edu <= Name of machine
Address: 129.62.148.8 <= IP address of machine

% nslookup 129.62.148.8 <= Reverse lookup
Server: ccis03.baylor.edu
Address: 129.62.16.4

Name: burro.baylor.edu
Address: 129.62.148.8

ifconfig Configure and display interface configuration

% ifconfig -a
lo        Link encap:Local Loopback
          inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
          UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
          RX packets:10714 errors:0 dropped:0 overruns:0 frame:0
          TX packets:10714 errors:0 dropped:0 overruns:0 carrier:0 coll:0

eth0      Link encap:Ethernet HWaddr 00:60:8C:EA:03:C8
         inet addr:129.62.149.74 Bcast:129.62.149.255 Mask:255.255.254.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:18935311 errors:12566 dropped:12566 overruns:0 frame:12566
          TX packets:10342456 errors:30 dropped:0 overruns:0 carrier:249 coll:30864
          Interrupt:10 Base address:0x300

traceroute - Print the route packets take to network host

% traceroute www.yahoo.com
traceroute to www1.yahoo.COM (204.71.200.66), 30 hops max, 40 byte packets
1 stugate6 (129.62.148.1) 7.953 ms 9.387 ms 0.886 ms
2 BORDER1-fa1-0-0.WACO.TX.VERIO.NET (128.241.72.1) 1.065 ms 0.988 ms 1.093ms
3 HOU1-S33.SESQUI.NET (128.241.7.209) 10.409 ms 10.22 ms 10.12 ms
4 fe0-1-0.iah0.verio.net (129.250.30.209) 11.826 ms 10.577 ms 10.304 ms
5 iah0-0.dfw1-0.verio.net (129.250.2.81) 15.841 ms 16.314 ms 15.554 ms
6 dfw1.dfw2.verio.net (129.250.2.162) 17.436 ms 15.607 ms 15.777 ms
7 dfw2.iad3.verio.net (129.250.2.210) 59.788 ms 59.44 ms 62.142 ms
8 iad3.iad0.verio.net (129.250.2.177) 60.357 ms 59.524 ms 60.014 ms
9 s0-0-1.br1.DCA.globalcenter.net (206.165.113.145) 59.706 ms 63.32 ms 60.876 ms
10 pos6-0-0-155M.cr1.IAD.globalcenter.net (204.152.166.6) 64.315 ms 60.805 ms 61.49 ms
11 fe4-1.cr2.IAD.globalcenter.net (204.152.166.162) 62.767 ms 62.994 ms 64.69 ms
12 104.atm1-1-0.br1.NUQ.globalcenter.net (206.251.4.61) 188.249 ms 192.149 ms 200.304 ms
13 pos0-1-155M.cr1.NUQ.globalcenter.net (206.132.160.25) 211.402 ms 220.327 ms 247.491 ms
14 pos1-0-622M.cr1.SNV.globalcenter.net (206.251.0.74) 207.242 ms 198.57 ms 187.632 ms
15 pos4-0-0-155M.hr5.SNV.globalcenter.net (206.251.0.197) 197.637 ms 198.819 ms 198.337 ms
16 www1.yahoo.com (204.71.200.66) 193.683 ms 206.884 ms 200.106 ms

telnet - Connect (TCP) to a specific machine/port. You can use it to play with services other than telnet (Look in /etc/services for list of services):

Echo (Port 7)- Echo back what you type

% telnet plum echo

Trying 129.62.148.2...

Connected to PLUM.baylor.edu.

Escape character is '^]'.

hello

^] (Hit Cntl-] to get to exit to telnet prompt)

telnet> quit

Connection closed.

Daytime (Port 13) - Send time of day

% telnet plum daytime

Trying 129.62.148.2...

Connected to PLUM.baylor.edu.

Escape character is '^]'.

Thu Feb 4 10:07:18 1999

Connection closed by foreign host.

HTTP (Port 80) - Connect to web server

% telnet plum www

Trying 129.62.148.2...

Connected to PLUM.baylor.edu.

Escape character is '^]'.

GET /

<HTML>

<HEAD>

<TITLE>School of Engineering and Computer Science</TITLE>

... (Deleted stuff)

</BODY>

</HTML>

Connection closed by foreign host.

arp - Display and change ARP (Address Resolution Protocol) cache

molar:/etc% arp -a
Address                 HWtype HWaddress           Flags Mask            Iface
stugate6                ether   00:90:AB:C2:A0:00   C     *               eth0
st-csi-a-dyn-01.baylor. ether   00:A0:C9:D7:5A:C5   C     *               eth0
plum.baylor.edu         ether   00:A0:C9:D7:2C:06   C     *               eth0
spud.baylor.edu         ether   00:20:AF:E8:EE:25   C     *               eth0
michaela.baylor.edu     ether   00:00:94:7B:09:3C   C     *               eth0
GL09.baylor.edu         ether   00:A0:C9:67:F4:8B   C     *               eth0
129.62.148.38           ether   00:A0:C9:D7:5A:E4   C     *               eth0
burro.baylor.edu        ether   00:00:94:75:45:13   C     *               eth0
GL14.baylor.edu         ether   00:A0:24:0C:42:B9   C     *               eth0
GL15.baylor.edu         ether   00:A0:24:0C:41:F5   C     *               eth0
GL16.baylor.edu         ether   00:A0:C9:67:F5:63   C     *               eth0
lisa.baylor.edu         ether   00:A0:C9:D7:2C:07   C     *               eth0

netstat - Display network connections, routing tables, and interface statistics

Network connections

% netstat -a | more

Active Internet connections (including servers)

Proto Recv-Q Send-Q Local Address Foreign Address State

... (deleted stuff)

tcp 0 0 *:ftp *:* LISTEN (Waiting FTP Server)

... (deleted stuff)

tcp 0 0 michaela.baylor.:telnet lisa.baylor.edu:2733 ESTABLISHED (Telnet connection)

... (deleted stuff)

Active UNIX domain sockets (including servers)

Proto RefCnt Flags Type State I-Node Path

... (deleted stuff)

unix 1 [ ACC ] STREAM LISTENING 1331 /dev/printer

... (deleted stuff)

Routing tables

% netstat -r

Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

129.62.148.0 * 255.255.254.0 U 1500 0 0 eth0

127.0.0.0 * 255.0.0.0 U 3584 0 0 lo

default bulan2-e1.baylo 0.0.0.0 UG 1500 0 0 eth0

Interface statistics (similiar to ifconfig)

% netstat -i

Kernel Interface table

Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flags

lo 3584 0 24 0 0 0 24 0 0 0 BLRU

eth0 1500 0 BRU

route - Show / manipulate the IP routing table

Showing routing table

% route

Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface

129.62.148.0 * 255.255.254.0 U 0 0 45 eth0

127.0.0.0 * 255.0.0.0 U 0 0 3 lo

default bulan2-e1.baylo 0.0.0.0 UG 0 0 66 eth0

Tracing route to machine on same subnet
% traceroute lisa
traceroute to LISA.baylor.edu (129.62.148.15), 30 hops max, 40 byte packets
1 lisa (129.62.148.15) 0.469 ms 0.349 ms 0.345 ms

Manipulating routing table

% route add -host lisa gw bulan2-e1

Showing updated routing table

$ route

Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface

lisa.baylor.edu bulan2-e1.baylo 255.255.255.255 UGH 0 0 1 eth0

129.62.148.0 * 255.255.254.0 U 0 0 46 eth0

127.0.0.0 * 255.0.0.0 U 0 0 4 lo

default bulan2-e1.baylo 0.0.0.0 UG 0 0 66 eth0

Tracing new route to machine on same subnet

% traceroute lisa

traceroute to LISA.baylor.edu (129.62.148.15), 30 hops max, 40 byte packets

1 bulan2-e1 (129.62.148.1) 0.930 ms 0.810 ms 0.870 ms

2 lisa (129.62.148.15) 0.565 ms 0.513 ms 0.477 ms

URL Syntax