well, i have mentioned the basic setup that i have done and everything works fine with it and thus would suggest you to do the same thing.
First of all you need to access the router via http://192.168.1.1 and input the default username and password. Once you completed with it you have to then click on Basic, then WAN in the left hand menu, and in the window select configured the following mentioned settings.
Code:
VPI = 0
VC = 38
Active = Yes
Mode = Routing
Encapsulation = PPPoA (PPP over ATM)
Multiplex = VC
Username = as provided by your ISP
Password = *as provided by your ISP
Default Route = Enable
NAT = Enable
Obtain an IP Address Automatically = Green Dot (Enabled)
IP Address, Subnet Mask, Gateway all = 0.0.0.0
Connect on Demand: Max Idle Timeout = No green dot
Nailed-Up Connection = Green dot (Enabled)
TCP MSS for TT = 1392 For BT = 1418
MTU For TT = 1432 For BT = 1458
RIP = Disable
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