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Abnormal NE Login Caused by Incorrect NE Subnet Mask

Publication Date:  2012-07-25 Views:  60 Downloads:  0
Issue Description
Coutry Z, one hop of Microwave link interconnected by RTN 950 (V1R3), DCN adopts the Inband IP soultion.

When the commissioning personnel is trying to login to the NE 9-8 through theWeb LCT, and found there is something abnormal. When the ODU is power off, the login is successful, but when the ODU is power on, the login is failed. The commissioning personnel calls the person at the other end, NE 9-9, the person at the NE 9-9 site does the same operaion, the Login is normal regardless of the ODU status.
Alarm Information
No alarms



Handling Process
Modify the submask of NE 9-8 as 255.255.255.0, and fault is removed.
Root Cause
1. This is a local login fault, so there is no business with the Microwave link itself.

2. Since it is a fault of communication, so communication parameters should be firstly check and the following information is got:

NE 9-8   NE IP: 10.109.1.8 Submask: 255.255.0.0
NE 9-9   NE IP: 10.109.1.9 Submask: 255.255.255.0
Laptop IP:10.109.1.125 Submask: 255.255.255.0

3. Check the IP routing table, and pick out the two key items as follow:



 4. As we know, when Weblct on the laptop logins into the NE 9-8, the laptop sends out the packet to the NE 9-8, and the NE 9-8 sends back a reply packet according to the routing foward table, and right now as shown above in the route table ,there are two available pieces of routing, 10.109.0.0/16 and 10.109.1.0/24, and the corresponding interface are NMS port (Etherent1) and Microwave link(Serial2), based on the longest match principle, 10.109.1.0/24 is the final option, and the reply packet is forwarded to Serial2 but not Ethernet1, in another word, the laptop can not receive the reply packets, and the Weblct login fails.
Suggestions
DCN parameters should be uniformly planned and carefully configured.






END