My Internet connection is not stable after recent firmware upgrade, what is the problem?

Released in firmware version 1.10.01.201, we introduced a new Automatic MTU (Maximum Transmit Unit) feature. However, we found some cable modem might be giving a very small MTU value and that will cause Internet access problem. If you found similar symptom, please follow below Troubleshooting instruction for “cannot connect to Internet” and change the MTU setting accordingly.