I had a BSNL broadband connection with ZTW ADSL router previously and new connection is with Airtel Broadband. I tried to use ZTE router, but it failed to ‘up’ connection each and every time. So finally used Beetal Modem for connection and ZTE as Wireless router only. Today found solution for that. Problem was with ATM PVC (VPI/VCI) setting
“To go a bit technical, the ATM interface should be configured as point to point with the matching ISP VPI/VCI value. The reason behind it is that there is possibility of having multiple VPI/VCI values within the same ATM interface. By setting a sub-interface as point-to-point connection with specific VPI/VCI value, the ADSL modem will know how it correctly forwards traffic to proper path.” – http://www.dslreports.com/faq/13865
BNSL ZTE ADSL router:
VPI – 0
VCI – 35
VPI – 1
VCI – 32
So, if need to use BSNL <>Airtel router, then update required for VPI/VCI Settings otherwise connection will not up.