At a one network site,
ME60s are upgraded from V600R006C00SPC300 to V600R008C10SPC300 and then restarted. Before the upgrade, the OSPF status
of all interfaces is Full. After the upgrade, some interfaces remain in the
Exchange state and cannot establish a neighbor relationship with an ME60.
The status of the corresponding interface
remains in the Exchange state and cannot be changed to Full.
1. Ping the device to check the link status. The ping succeeds. Therefore,
the interface connectivity on the ME60s after the upgrade is normal.
2. Compare the configurations of the device
interfaces at both ends. It is found that the OSPF configurations, such as the
MTU, addresses, OSPF authentication, and network advertisement address, are consistent.
3. Run the disp ospf error command. It is
found that 135 errors with the type of Unknown neighbor exist.
4. Delete the OSPF authentication
information from interfaces at both ends and then reconfigure the OSPF
authentication. The problem persists.
5. Enable the debugging function on the ME60s and
collect OSPF information. It is found that the corresponding interface receives
information from the target device. The MTU value is 1548, indicating that OSPF
packet exchanges have reached the LSA-U stage.
6. Based on the preceding information and
the OSPF packet exchange process, if the link status is normal, the problem may
arise from incorrect OSPF configurations. Because the authentication
information has been modified, delete the MTU from the ME60 interfaces. After
that, the OSPF status of the corresponding interfaces is changed to Full and
the OSPF neighbor relationship can be properly set up.
Based on the OSPF error analysis and
debugging analysis, Hello packets have been exchanged to set up OSPF neighbor
relationships, and the OSPF neighbor status is changed as follows: init -> 2-way
-> Exstart -> Exchange. .In the Exchange state, when routers exchange DD
packets containing the link status information, negotiation fails between the
two ends. As a result, the OSPF neighbor relationship fails to be set up. Packet
discarding occurs because the receive end cannot process the DD packets
received from the transmit end during DD packet exchanging. In addition, the
ME60s are on the live network and therefore involves exchanges of lots of DD
packets. When the local ME60 interface sends data packets carrying the
configured MTU, the peer device cannot properly receive the packets. Such
packets are discarded. Therefore, the OSPF neighbor relationship fails to be
Additionally, it is doubted that the actual MTU on the peer device is
inconsistent with the configured MTU. When the default MTU is used to receive
data, the data packets received from the local device are sent based on the
configured MTU. The peer device cannot receive such packets and therefore the
data packets are discarded.
Delete the MTU configuration from the local interface and configure the ME60s
to send data packets with the default MTU settings.
After the OSPF peer status is changed to
Exchange, put the focus on interfaces' MTU configuration and OSPF
configuration. Modify the MTU and OSPF configuration as required and locate the
root cause of the problem.