Problems in WLAN Ubuntu 12.04 LTS

Question

I have problems in connecting to internet via my WLAN.

I had ubuntu 10.04 LTS initially which I recently upgraded to 12.04 LTS, the problem existed from the earlier version.

I can connect to internet with a ethernet.

I am able to scan for the available WLANs. Also I can connect to a WLAN of my choice. But I am unable to access internet.

So I am afraid I might have misconfigured something. Any pointers on what would have went wrong ?.

Additional Information:

$nm-tool 

NetworkManager Tool

State: connected (global)

- Device: wlan0  [MyWLAN] --------------------------------------------------------
  Type:              802.11 WiFi
  Driver:            iwlwifi
  State:             connected
  Default:           yes
  HW Address:        00:1E:65:94:11:86

  Capabilities:
    Speed:           6 Mb/s

  Wireless Properties
    WEP Encryption:  yes
    WPA Encryption:  yes
    WPA2 Encryption: yes

  Wireless Access Points (* = current AP)
    MyWLAN5:           Infra, 00:24:01:38:BC:6B, Freq 5240 MHz, Rate 54 Mb/s, Strength 54 WPA WPA2
    ...................
    ...................

    SSFWLAN:         Infra, 00:16:01:AF:38:33, Freq 2422 MHz, Rate 54 Mb/s, Strength 24 WPA
    AndroidAP:       Infra, 04:46:65:4A:B6:5D, Freq 2437 MHz, Rate 54 Mb/s, Strength 97 WPA
    *MyWLAN:           Infra, 00:24:01:38:BC:69, Freq 2457 MHz, Rate 54 Mb/s, Strength 75 WPA WPA2

  IPv4 Settings:
    Address:         192.168.0.154
    Prefix:          24 (255.255.255.0)
    Gateway:         192.168.0.1

    DNS:             192.168.0.1


- Device: eth0 -----------------------------------------------------------------
  Type:              Wired
  Driver:            e1000e
  State:             unmanaged
  Default:           no
  HW Address:        00:22:68:11:D4:F8

  Capabilities:
    Carrier Detect:  yes
    Speed:           100 Mb/s

  Wired Properties
    Carrier:         on

---

$ lspci -nnk | grep -iA2 net
00:19.0 Ethernet controller [0200]: Intel Corporation 82567LF Gigabit Network Connection [8086:10bf] (rev 03)
    Subsystem: Lenovo Device [17aa:20ee]
    Kernel driver in use: e1000e
--
03:00.0 Network controller [0280]: Intel Corporation PRO/Wireless 5100 AGN [Shiloh] Network Connection [8086:4237]
    Subsystem: Intel Corporation WiFi Link 5100 AGN [8086:1211]
    Kernel driver in use: iwlwifi

---

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG        0 0          0 wlan0
0.0.0.0         192.168.0.1     0.0.0.0         UG        0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan0

---

$ ping -c4 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
From 192.168.0.172 icmp_seq=1 Destination Host Unreachable
From 192.168.0.172 icmp_seq=2 Destination Host Unreachable

--- 192.168.0.1 ping statistics ---
4 packets transmitted, 0 received, +2 errors, 100% packet loss, time 3005ms
pipe 2

$ ping -c4 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=50 time=39.3 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=50 time=121 ms
64 bytes from 8.8.8.8: icmp_req=3 ttl=50 time=41.9 ms
64 bytes from 8.8.8.8: icmp_req=4 ttl=50 time=37.8 ms

--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3002ms
rtt min/avg/max/mdev = 37.808/60.048/121.087/35.271 ms