Sometimes, AR4640A cannot telnet, sometimes it can.
1. Sometimes, AR4640A router can telnet, which means the configuration is out of problem, and no limitation is involved over telnet on links.
2. It is communicated as doing ping for AR4640 interface address, which means the links are out of problems.
3. Because there is layer 2 LanSwitch between AR4640A and AR4640Bd, and this LanSwitch connects with other layer 3 device too, which means the IP address maybe conflicts.