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#1 Posted : Tuesday, January 30, 2024 2:42:54 PM(UTC)

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Groups: Registered
Joined: 5/23/2022(UTC)
Posts: 22

Issue description
At a site, an HG8245H connected to an Huawei MA5800 OLT is connected to a user through Wi-Fi. The Wi-Fi speed test does not meet the requirement.

Handling Process
The possible causes are as follows:

1. The performance of the speed test terminal is poor.

2. The rate limit configuration is incorrect.

3. The upper-layer network is faulty.

After receiving the problem, check the problem one by one according to the preceding roadmap.
1. Replace the ONT and PC. It is found that the fault persists. Therefore, the fault is not caused by the terminal.

2. Change the Wi-Fi access mode to wired access mode. Continue the test with the same account. It is found that the rate limit can be met.

3. According to the preceding two test steps, it is suspected that the ONT Wi-Fi performance is abnormal or the Wi-Fi channel is interfered with. However, the same ONT and PC are connected to another OLT in the same equipment room and continue to access the network through Wi-Fi. The test result shows that the rate limit is normal. This eliminates wifi performance and channel interference.

4. Analyze the forwarding statistics of the faulty OLT. It is found that the upstream port of the OLT receives a large number of broadcast packets. (xe0 corresponds to port 0/18/1) , close to the peak value of the default value of broadcast suppression on the upstream port of the OLT. (The default value is 7, indicating that 763 broadcast packets are allowed to pass through.)

Current broadcast suppression traffic: 7

Current multicast suppression traffic: 7

Current unknown unicast suppression traffic: 7

5. Mirror traffic on the upstream port locally. It is found that a large number of ARP broadcast packets are received from the same device on the network, and the VLAN is also the service VLAN.

6. Trace the source MAC address of the ARP broadcast packet on the upper-layer switch. After the user is found, isolate the network. Then test the Wi-Fi rate on the OLT. The rate can meet the rate limit requirements.

Root cause
A network-side device abnormally sends a large number of broadcast packets. In a Wi-Fi system, broadcast packets are management frames and are transmitted at a low rate. A large number of such packets occupy a large number of air interface resources and a part of bandwidth, affecting a rate test.

Find the source MAC address of the broadcast packet through local mirroring, trace the user with this MAC address on the upper-layer switch, and isolate the MAC address.
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