NE40 and J client connect POS interface back-to-back. The distance of two device is five meters. POS interface of NE40 is up and the protocol is down.
1. Check the CRC correction of two interfaces. Whether it scrambles or clock configuration is right. They are not problematic.
2. Confirm fiber mode of two interfaces. Single-mode is 15km and fiber power is within the range.
3. Enable physical loop for NE40pos from distant end. With display interf pos check whether there is output information of loopback is detected. If there is such information, the interface and physical link are normal.
4. Check three steps above, the physical is up and the protocol is down. Open debug lpu slotid ppp command and it is found that there is only output packet but no input packet.
5. Check whether POS interface of J client is normal or not. They are not problematic.
6. Through display pos interf pos */*/* it is found that POS interface of J client sends C2 and the byte is 0xcf. Change C2 of POS interface at NE40 as 0xcf and the problem is solved.
The match or mismatch of c2 bit is mainly to control link light of POS interface. C2 acts as identifier and not influence service. When C2 and J client connect POS interface, it must match C2 bit. Otherwise the physical interface is up and the protocol is down.