Ping: bad address ''

I am using Colibri VF61 and voila carrier board. I am using wavecom modem for gprs. I have initiated gprs using the following url:
Embedded Linux Systems - GSM/3G/4G
I am getting an interface ppp0 but I am not able to ping. I am getting bad address ‘’ error. What am i missing ?

Did you setup the DNS in /etc/resolv.conf?

I have configured DNS. My /etc/resolve.conf looks like : nameserver
Still, I am getting the same error.

Can you ping the DNS server?