1)
a) dig (domain information groper) – is a flexible tool for interrogating DNS name servers.
b) nslookup – Queries a name server for a host or domain lookup.
c) host – DNS lookup uility.

The below example shows the information like CNAME , Aliases, ipaddres , etc about www.google.com

a) dig
bash-2.05b# dig www.google.com

; <<>> DiG 9.2.4 <<>> www.google.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1088
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 7, ADDITIONAL: 0

;; QUESTION SECTION:
;www.google.com. IN A

;; ANSWER SECTION:
www.google.com. 585119 IN CNAME www.l.google.com.
www.l.google.com. 69 IN A 216.239.51.99
www.l.google.com. 69 IN A 216.239.51.104

;; AUTHORITY SECTION:
l.google.com. 60734 IN NS g.l.google.com.
l.google.com. 60734 IN NS b.l.google.com.
l.google.com. 60734 IN NS f.l.google.com.
l.google.com. 60734 IN NS c.l.google.com.
l.google.com. 60734 IN NS a.l.google.com.
l.google.com. 60734 IN NS e.l.google.com.
l.google.com. 60734 IN NS d.l.google.com.

;; Query time: 2 msec
;; SERVER: 10.5.50.184#53(10.5.50.184)
;; WHEN: Sun Feb 3 09:51:46 2008
;; MSG SIZE rcvd: 196

b) host

bash-2.05b# host www.google.com
www.google.com is an alias for www.l.google.com.
www.l.google.com has address 216.239.51.104
www.l.google.com has address 216.239.51.99

c) nslookup

bash-2.05b# nslookup www.google.com
Server: 10.5.50.184
Address: 10.5.50.184#53

Non-authoritative answer:
www.google.com canonical name = www.l.google.com.
Name: www.l.google.com
Address: 216.239.51.99
Name: www.l.google.com
Address: 216.239.51.104

infconfig -a
bash-2.05b# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:11:43:32:49:99
inet addr:10.2.150.74 Bcast:10.5.50.127 Mask:255.255.255.192
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:357854361 errors:0 dropped:0 overruns:0 frame:0
TX packets:383621806 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3168219417 (3021.4 Mb) TX bytes:3724305382 (3551.7 Mb)
Interrupt:17

eth1 Link encap:Ethernet HWaddr 00:11:43:32:49:9A
inet addr:10.5.154.138 Bcast:10.5.54.127 Mask:255.255.255.128
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Interrupt:18

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:92809439 errors:0 dropped:0 overruns:0 frame:0
TX packets:92809439 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1454141744 (1386.7 Mb) TX bytes:1454141744 (1386.7 Mb)

3) To find more information about a network interface, the below example shows detail information about interface eth0.

bash-2.05b# ethtool eth0

Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: Not reported
Advertised auto-negotiation: No
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: off
Supports Wake-on: d
Wake-on: d
Link detected: yes