Description: NE40/E500/C6509 are connected through GE port at L3, running OSPF; E500 works at transparent mode.
Symptoms: OSPF neighbor flaps when both NE40 and E500 ping C6509 until stopped, but the ARP entries could be learned in disruption.
1. Change the negotiation mode of both sides, and the problem persists.
2. Measure the optical power, and it is normal.
3. Change the optical interface and tail fiber of E500/C6509, and the problem persists.
4. Disconnect NE40, and connect E500 to C6509 independently, without flap in connection; ignore E500, and connect NE40 to C6509 independently, but flap occurs again, so it is located that NE40 is problematic.
5. According to packets captured in connection between NE40 and C6509 without E500, it is found that NE40 has transmitted STP packets to C6509 (C6509 enables STP, but NE40 does not), so C6509 congests the interconnecting ports, resulting in disruption. C6509 will calculate STP to enable the ports for connection, and then disable it later.
6. Through checkup, NE40 is at version 2317, without patch loaded; find the SP03 patch on FTP, and load it, solving the problem.
1. Port negotiation cause.
2. Optical power cause.
3. Optical interface or tail fiber cause.
4. Other reasons.
Disconnection because of STP is very common, and it is often caused by L2 loop. NE40 at 2317 will send the STP packets from the peer back if it is not loaded with patch, congesting the ports.