@pram
Doesn't really matter which router as long as its plugged into the affected line.
Basically there may (or may not) be a line stats page on the router, and you'll generally be most interested in any of the counters with "error" in their name, things like :
BER Errors (Bit Error Rate)
CRC Errors (Cyclic Redundancy Check)
FEC Errors (Forward Error Correction )
HEC Errors (Header Error Check)
What you want to do is make a (rough ballpark) note of the errors at T1 ... then go away for a reasonable Tx (maybe to make some tea
) ... come back and T2 and see which (if any) have incremented and the extent of the increments.
The faster the numbers whizz up, the more likely a line fault .... if they are only incrementing modestly then it may just be nothing to worry about.
The counters won't tell you much about non-physical related issues, such as things happening the ISP network once it hits the exchange.