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Abnormality of Interconnection Between the NE80 and the C12000 Due to the Mismatch of the C2 Bytes at the 2.5GB POS Interface

Publication Date:  2012-07-27 Views:  38 Downloads:  0
Issue Description
After the NE80 is power on, the GE interface and 155 MB interfaces run normally, but the 2.5 GB POS interface is still Down. 
Alarm Information
Query the system log. The following alarms are generated:
SRM/1/LabelMismatch:OID=1.3.6.1.4.1.2011.2.17.0.145,Index=67109638,SlotNum=7,SubCardNum=0,PortNum=0, receive path signal label mismatch! 
 
Handling Process
To fix the fault, adjust the C2 byte at the NE80 POS interface to be consistent with that at the C12000 POS interface by running the flag c2 207 command.
The commands are as follows:
interface Pos7/0/0
undo shutdown
link-protocol hdlc
flag c2 207
undo scramble
ip address *.*.*.* 255.255.255.252 
 
Root Cause
Because of the variances between the configurations of the NE80 POS interface and that of the C12000 in the encapsulation mode at the link layer, CRC check, and link scramble, you shall check the configurations one by one to ensure the consistency of the configurations.
1. For the encapsulation mode at the link layer, the default link layer protocols of the C12000 and the NE80 are HDLC and PPP respectively. The link layer protocols of the two devices shall be consistent. Check the configurations of the two devices at both ends. The link layer protocol of the NE80 is configured with HDLC. Set it to HDLC to avoid the possibility of the abnormality caused by the inconsistency of link layer protocols.
2. For the CRC check, the default CRC check bits of the C12000 and the NE80 are 16 bits and 32 bits respectively. Because the CRC check bits of the NE80 cannot be modified, the only way to ensure the consistency of the CRC check is to modify the CRC check bits of the C12000 to 32 bits. Check the configuration of the C12008. The CRC check bits are already modified by running the crc 32 command. Set it to 32 to avoid the possibility of the abnormality caused by the inconsistency of CRC check.
3. For the POS link scramble, the C12000 is not scrambled by default, but the NE80 is scrambled by default.The link scramble of the two devices shall be adjusted to be consistent. Check the configurations of the link scramble at the two devices. The scramble at the NE80 is already disabled, and thus the possibility of the abnormality caused by the inconsistency of link scramble is excluded.
4. For the POS physical layer encapsulation, the default encapsulation modes of the C12000 and the NE80 are SONET and SDH respectively. The inconsistency of the physical layer encapsulation does not affect the running of the protocol and the data forwarding because SONET and SDH are compatible. In the actual implementation of the engineering project, you are recommended to adjust the encapsulation modes to be consistent. Modify the default encapsulation mode at the NE80 interface to SONET. However, the fault still exists. Therefore, the possibility of the abnormality caused by the inconsistency of the encapsulation modes is excluded.
5. Check the detailed information about the NE80 interface by running the dis inter pos 7/0/0 ver command:
SDH overhead:(Rx/Tx)
F1 : NA/NA , J0 : 0x48/0x4e, K1 : 0x00/0x00, K2 : 0x00/0x00
S1 : 0x0f/0x08, C2 : 207/0x16, F2 : NA/NA , Z3 : NA/NA
The above information shows that the C2 bytes received does not match those sent. The C2 received from the C12000 is 207, which is different from 0x16. This is the reason why the interface cannot go Up. 
 
Suggestions
The 155 MB POS interface belongs to the low-speed POS interface. The NE80 does not check the C2 value of the low-speed POS interface. Therefore, although the C2 values at the two devices are different, the interface can be initiated normally. The 2.5 GB POS interface belongs to the high-speed POS interface. The NE80 checks the C2 value of the high-speed POS interface. Therefore, the inconsistency of the C2 values at the two devices causes the interface to be unable to turn Up normally. Thus the C2 values of the high-speed interfaces must be adjusted to be consistent. 

END