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Tuesday, September 17, 2013

Communication Commands In Linux

Network is one of the Important aspect. Linux Provides various commands in analyzing the network information

host
Searches for information about an Internet host by name or IP address, using DNS.

[root@vx111a ~]# host www.google.com
www.google.com is an alias for www.l.google.com.
www.l.google.com has address 74.125.236.82
www.l.google.com has address 74.125.236.83
www.l.google.com has address 74.125.236.84
www.l.google.com has address 74.125.236.80
www.l.google.com has address 74.125.236.81

ipcalc
Displays IP information for a host. With the -h option, ipcalc does a reverse DNS lookup, finding the name of the host (server) from the IP address.

[root@vx111a ~]# ipcalc -h 10.5.11.119
HOSTNAME=vx111a.example.com
nslookup
Do an Internet "name server lookup" on a host by IP address. This is essentially equivalent to ipcalc -h or dig -x . The command may be run either interactively or noninteractively, i.e., from within a script.

The nslookup command has allegedly been "deprecated," but it is still useful.

[root@vx111a ~]# nslookup -sil 10.5.11.119
Server: 202.54.12.164
Address: 202.54.12.164#53

** server can't find 119.11.5.10.in-addr.arpa.: NXDOMAIN

dig (Domain Information Groper)
Similar to nslookup, dig does an Internet name server lookup on a host. May be run from the command-line or from within a script.

Some interesting options to dig are +time=N for setting a query timeout to N seconds, +nofail for continuing to query servers until a reply is received, and -x for doing a reverse address lookup.
[root@vx111a ~]# dig -x 173.229.135.72

; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> -x 173.229.135.72
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- 42360="" font="" id:="" noerror="" opcode:="" query="" status:="">
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4

;; QUESTION SECTION:
;72.135.229.173.in-addr.arpa. IN PTR

;; ANSWER SECTION:
72.135.229.173.in-addr.arpa. 7200 IN PTR eth0.vx1379.nova.com.

;; AUTHORITY SECTION:
135.229.173.in-addr.arpa. 7200 IN NS eth0-DNS.omdx1ccf.nova.com.
135.229.173.in-addr.arpa. 7200 IN NS eth0-DNS.omhq1cce.nova.com.
135.229.173.in-addr.arpa. 7200 IN NS eth0-DNS.omdx1cd0.nova.com.
135.229.173.in-addr.arpa. 7200 IN NS eth0-DNS.omhq1cd8.nova.com.

;; ADDITIONAL SECTION:
eth0-DNS.omdx1ccf.nova.com. 7200 IN A 167.132.254.233
eth0-DNS.omdx1cd0.nova.com. 7200 IN A 167.132.254.237
eth0-DNS.omhq1cce.nova.com. 7200 IN A 167.132.254.225
eth0-DNS.omhq1cd8.nova.com. 7200 IN A 167.132.254.229

;; Query time: 3 msec
;; SERVER: 167.132.254.225#53(167.132.254.225)
;; WHEN: Tue Sep 17 07:52:28 2013
;; MSG SIZE rcvd: 271

traceroute
Trace the route taken by packets sent to a remote host. This command works within a LAN, WAN, or over the Internet. The remote host may be specified by an IP address.

[root@vx111a ~]# traceroute 10.5.11.119
traceroute to 10.5.11.119 (10.5.11.119), 30 hops max, 40 byte packets
1 vx111a.example.com (10.5.11.119) 0.047 ms 0.016 ms 0.013 ms

ping
This is a diagnostic tool for testing network connections, and it should be used with caution.

[root@vx111a ~]# ping 10.5.11.119
PING 10.5.11.119 (10.5.11.119) 56(84) bytes of data.
64 bytes from 10.5.11.119: icmp_seq=1 ttl=64 time=0.031 ms
64 bytes from 10.5.11.119: icmp_seq=2 ttl=64 time=0.032 ms

--- 10.5.11.119 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.031/0.031/0.032/0.005 ms

whois
The WHOIS system is used by domains and ip address on the Internet. It is used by system administrators to obtain contact information for IP address assignments or domain name administrators

[root@vx111a ~]# dnsdomainname
example.com
[root@vx111a ~]#whois google.com
Registrant:
Dns Admin
Google Inc.
Please contact contact-admin@google.com 1600 Amphitheatre Parkway
Mountain View CA 94043
US
dns-admin@google.com +1.6502530000 Fax: +1.6506188571

Domain Name: google.com

Registrar Name: Markmonitor.com
Registrar Whois: whois.markmonitor.com
Registrar Homepage: http://www.markmonitor.com

Administrative Contact:
DNS Admin
Google Inc.
1600 Amphitheatre Parkway
Mountain View CA 94043
US
dns-admin@google.com +1.6506234000 Fax: +1.6506188571
Technical Contact, Zone Contact:
DNS Admin
Google Inc.
2400 E. Bayshore Pkwy
Mountain View CA 94043
US
dns-admin@google.com +1.6503300100 Fax: +1.6506181499

Created on..............: 1997-09-15.
Expires on..............: 2020-09-13.
Record last updated on..: 2013-02-28.

Domain servers in listed order:

ns2.google.com
ns1.google.com
ns4.google.com
ns3.google.com

finger
Retrieve information about users on a network. 

[root@vx111a ~]#finger
Login Name Tty Idle Login Time Office Office Phone Host
root root pts/0 38d Aug 9 12:39 (eth0.vx181d.nova.com)
root root pts/1 38d Aug 9 14:58 (eth0.vx181d.nova.com)
root root pts/2 23:45 Sep 16 08:10 (eth0.vx181d.nova.com)
root root pts/3 Sep 17 07:19 (eth0.vx181d.nova.com)

We can also obtain more information about a user like
[root@vx111a ~]# finger root
Login: root Name: root
Directory: /root Shell: /bin/bash
On since Fri Aug 9 12:39 (CDT) on pts/0 from eth0.vx181d.uprr.com
38 days 19 hours idle
On since Fri Aug 9 14:58 (CDT) on pts/1 from eth0.vx181d.uprr.com
38 days 16 hours idle
On since Mon Sep 16 08:10 (CDT) on pts/2 from eth0.vx181d.uprr.com
23 hours 46 minutes idle
On since Tue Sep 17 07:19 (CDT) on pts/3 from eth0.vx181d.uprr.com
New mail received Tue Sep 17 04:02 2013 (CDT)
Unread since Tue Sep 17 01:29 2013 (CDT)
No Plan.

nc
It may be useful to know which ports are open and running services on a target machine

nc -z -v -n xxx.xxx.xxx.xx 10000-10020
provides information of the Open Ports On A Remote Machine ( xxx.xxx.xx.xx)

chfn
Change information disclosed by the finger command. If we want to change any of the information that is display when we run the finger command, we can use this command

wget
wget is a Utility is the best option to download files from internet. wget can pretty much handle all complex download situations including large file downloads, recursive downloads, non-interactive downloads, multiple file downloads etc.


scp
scp (Secure CoPy) is a secure and network-aware version of the UNIX rcp remote copy command and allows files to be transferred between different computers via an encrypted end-to-end link

scp $PWD/filename username@host:/path/to/other/destination/directory

ssh
ssh is used to connect into a remote machine and for executing commands on a remote host.
ssh user@hostname [command]


More to Come , Happy learning :-)

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