Topology: NE40 --NE40--S2403H --PC
MA5200F is at MA2.10-7127, and NE40 is at VRP3.10-0420. The individual users change to use PPPOE dialup to access network from the original static IP address. In the test after cutover, users access network through dialup by PPPOE dialing software. If they drop offline abnormally, they cannot come online through dialup in short time.However, after a long interval, the dialup is normal. After many times tests, the problem persists.
Check the delay of MA5200F, and it is configured as ppp keepalive interval 120 retransmit 5. It means that the handshaking interval for detecting users of MA5200F is 120 seconds, and the handshaking times to detect users are 5. As a result, when M5200F users have been dropped offline for 600 seconds (10 minutes), the users will be released, and they can come online through dialup.
Set the handshaking time to 20 seconds, and handshaking times to 3 (the default value of system, command is 'ppp keepalive' under virtual template view ). The delay of 1 minute is acceptable for users. After the modification, the problem has been solved.
Use Sinffer to capture packets. Through analysis over PPPOE packets, it is found that when the users drop offline abnormally, and they dial up at once, the PADI packets sent by PC get no response; in other words, the BAS device (MA5200F) does not use PADO packets to respond user PC. Therefore, the user PC and MA5200F have lost contact in PPPOE discovery stage. If dialing up after a long interval, MA5200F use PADO packets to respond user PC, and PPPOE connection sets up normally; users can come online.
After the analysis above, it is concluded that once the users drop or get offline abruptly, MA5200F regard they are still online because of delay, so when the users dial up again, they cannot come online normally.