NE5000E(POS1/0/1,10.0.0.1/24 )---------(POS1/0/1,10.0.0.2/24 )Sxxx.
NE5000E is connected to Sxxx of A company through 2.5GPOS, and sets up OSPF neighbor. NE5000E uses import command to import direct route, and it can ping to the loopback address of the peer, but it cannot ping to the address of interconnected interface at peer.
The product of A company has a special feature in realization of PPP: it does not create direct route with 32-octet mask for the direct interface of the local. It needs to configure static route manually, and set the priority to the highest; alternatively, use route policy to disable the distribution of corresponding route or being learned.
As of POS port, NE5000E creates three direct routes: 10.0.0.0/24, 10.0.0.1/32 (tagged as non-distribute), 10.0.0.2/32 (tagged as distributed). When NE5000E is configured with direct route, 10.0.0.2/32 will be imported, and External LSA will be created and transmitted out. Sxxx does not create 10.0.0.2/32, so when it receives the LSA of 10.0.0.2/32, it will calculate an OSPF route which will be elected as optimal for forwarding. The next hop of the route is the POS port of NE5000E. When both ping the direct address of each other, the packets sent to 10.0.0.2 are forwarded back by Sxxx; the packets are discarded when TTL expires, the address of direct-connected interface cannot be pinged to .