Debarshi,
[root@Sunflower ~]# route add -net 192.168.0.0 netmask 255.255.255.0 gw ipx4 ipx4: Host name lookup failure [root@Sunflower ~]#
If your DNS doesnt know how to resolve ipx4 to an IP you shall get Host name lookup failures.
Try replacting ipx4 with IP on your external Interface.
Thanks & Regards, Mitul Limbani, Founder & CEO, Enterux Solutions, The Enterprise Linux Company (TM), www.enterux.com