The Negotiated Port Speed Is Only 100M Due to Bad Contact of the Adapter or Cable

Publication Date:  2015-07-03 Views:  198 Downloads:  0
Issue Description
Network Topology:

Figure 4-5 Networking diagram



Service Overview:
The firewalls are deployed transparently and work in load balancing mode to secure mobile phone access.

Symptom:

On Nov. 8, 2010, the switch S53-B port (0/0/41) connected to USG-2 was flapping (rotating between up and down state), and when the port was up, the speed was only 100M. After the firewall forced the speed to 1000M, services were restored.


Nov  8 2010 08:36:43 Lima-M2-Data-S5352-2 %%01IFNET/4/UPDOWN(l): The state of interface GigabitEthernet0/0/41 was changed to DOWN.
2010-11-08 08:36:44 Data-USG-2 %%01PHY/1/PHY(l):     GigabitEthernet0/0/2: change status to down
2010-11-08 08:36:44 Data-USG-2 %%01PHY/1/PHY(l):     GigabitEthernet0/0/0: change status to down
Nov  8 2010 08:36:45 Lima-M2-S9312-D %%01IFNET/4/IF_STATE(l): Interface GigabitEthernet10/0/5 has turned into DOWN state.


On Nov. 13, 2010, the switch S53-B port (0/0/41) connected to USG-1 was flapping (rotating between up and down state), and when the port was up, the speed was only 100M. As a result, not all traffic was forwarded (the total traffic exceeded 100 Mbps). After the firewall forced the speed to 1000M, services were restored.
Handling Process
1. Based on the networking diagram and the symptom, the fault might be caused by bad contact of the adapter.

2. A test was performed in the lab to verify whether the fault was caused by the bad contact of the adapter. During the test, a USG was connected to the S5352C and then a JuniperSSG550 was connected to the S5352C. When the adapter had a bad contact, the port was flapping, and the negotiated port was only 100M when the S5352C was connected to the USG and only 10M when the S5352C was connected to the JuniperSSG550. The symptom in the lab was the same as that on the live network.

3. The adapter had a bad contact due to wear and tear and caused the fault.

4. The field personnel tested the cables with a cable tester and found that that the connection was abnormal, proving that either the cable or the adapter was abnormal.

Figure 4-6 Test result


Root Cause
The fault was caused by the bad contact of the adapter or cable.
Solution
Remove the adapters and directly connect the cables to the USG to check whether the fault occurs. 

END