i tried to update my scientific linux and i am getting the following

yum update
Loaded plugins: fastestmirror, refresh-packagekit, security
Determining fastest mirrors
* sl: ftp.scientificlinux.org
* sl-security: ftp.scientificlinux.org
http://ftp.scientificlinux.org/linux...ta/repomd.xml: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'ftp.scientificlinux.org'"
Trying other mirror.

and ping, nslookup also not working. I can ping my network gateway. but can't ping google.com or any other ip address external to my proxy

Please help me with this problem

my ifconfig info is

# ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:46 errors:0 dropped:0 overruns:0 frame:0
TX packets:46 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3894 (3.8 KiB) TX bytes:3894 (3.8 KiB)

p2p1 Link encap:Ethernet HWaddr 00:25:64:48:1C:F8
inet addr:172.30.24.6 Bcast:172.30.27.255 Mask:255.255.252.0
inet6 addr: fe80::225:64ff:fe48:1cf8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:33943 errors:0 dropped:0 overruns:0 frame:0
TX packets:20310 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:24455882 (23.3 MiB) TX bytes:3257169 (3.1 MiB)
Interrupt:18