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Connection flapping between IPhones and AVAYA IPPBX using HUAWEI datacom infraestructure

Publication Date:  2015-09-05 Views:  244 Downloads:  3
Issue Description

Avaya IP-Phones lost connection with Avaya IPPBX several times during the day, connectivity between IPphones and IPPBX is through HUAWEI SW's S5700-52C-PWR-EI and S7706. So communication issues using HUAWEI devices should be discarded.

Issue started to happen after SW's were migrated from EXTREME to HUAWEI, so it seems an issue with HUAWEI's SW's.

Topology: Enclosed as attachment in this case

Handling Process

Communication flapping was random during the day so only way to troubleshoot is to monitor the network and wait for issue, also we started to check logs in SW's.

Basically  next points resume the handling process

 

1.- To check logs in SW's

2.- To monitor network, waiting for failure.

3.- To check logs of SW's during failure.

4.- To determine if there is an issue in configuration or is another kind of issue

5.- To do modification in configuration.

 

During the collection of logs we detected that every time that voice service was flapping, in logs of SW's is detected an STP topology change, so it seems an issue with STP, we started to check configuration related to STP in all SW and we didn't find any loop that could cause SW's CPU overload and packet discarding, so next step was to check status of SW were IP-PBX was connected, we found next configuration in the port connected to IP-PBX

stp edged-port enable

According with HEDEX description for above command is:

On a Layer 2 network running a spanning tree protocol, a port connected to terminals does not need to participate in spanning tree calculation. If the port participates in spanning tree calculation, the network convergence speed will be affected. In addition, status changes of the port may cause network flapping, interrupting user traffic. To address this problem, you can run the stp edged-port enable command to configure the port as an edge port. Then, the port will not participate in the spanning tree calculation. This speeds up network convergence and improves network stability.

Precautions

If a port of a switching device receives a BPDU after being configured as an edge port, the switching device will automatically set the port as a non-edge port and recalculate the spanning tree.

Configuration seems to be fine since the port is connected to a terminal, in this case the IPPBX, but we didn't know that IP-PBX was sending BPDU that's why after IP-PBX send BPDU the Switch automatically to non-edge port and it cause flapping in service.

Root Cause

IP-PBX was sending BPDU to the SW, so it was participating in STP root election process causing slow convergence and it was causing voice service flapping. 

Solution

To diable STP on the port that connect IP-PBX. in this way IP-PBX stoped to participate in STP election process.

command:

stp disable

END