OSPF is run between the AR46, NE20, and S8016. The S8016 sends default routes through OSPF, but the downstream PC connected to the AR46 cannot access the Internet.
1. It is confirmed that the PC hardware and the configuration are normal.
2. Check the OSPF configuration, and find that the configuration is normal and the neighbor status is also normal. Check the OSPF routing table of devices, and it is found that only OSPF default routes exist on the NE20 and explicit routes of OSPF are unavailable. Check the OSPF configuration on the NE20 again, and find that route filtering is set on the NE20. Only OSPF default routes can be learnt. The problem is located: When the downstream PC connected to the PC access external networks, packets can pass through. After the returned packet reaches the NE20, the packet is sent back to the S8016 because there are no explicit routes of OSPF. In this case, the packet is discarded until TTL is 0. Cancel route filtering on the NE20 and the downstream PC connected to the AR46 can access network.
1. The hardware of the PC and the configuration fail.
2. The OSPF configuration fails.