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moxa EDS-408a-MM-SC Cisco 3750X GLC-GE-100FX Slow Communication


I have been stress testing an Industrial network and found some issues. The client now wants me to fix the issues but i am running into some problems. 



The three networks,




All appear to be functioning correctly but under stress testing the networks fail.



The link between each port from the Cisco 3750x or the 2960S through to the moxa switches in the shelters are failing during the writing or the reading phase of a package. Under testing the switch will either write at full capacity (94mbps) and read at (2mbps) or vice versa, There is also the case that some switches are reading and writing ok.

I compared the configurations between the switches with no issues and the switches with the issues and there are no differences. 

To confirm the results I ran through the tests again and found that some if not all the results had changed. This means that the results that were produced a day earlier are not consistent.



While troubleshooting it appeared that some switches preferred the ports on the Cisco switch to set to Duplex Full instead of Automatic but others preferred the ports to be set at Auto Duplex.

Cleared all configurations from cisco and moxa and attempted to build the switch scripts back one part at a time. This didn’t affect the results.

Confirmation of Fibre and Patch cable type - all OM3 and good

Confirmation on the hardware and Firmware versions - All Cisco switches tested were of the correct hardware and firmware version for the GLC-GE-100FX SFP (known issues with non-supported hardware)

Confirmation of the SFP make and Model as GLC-GE-100FX (Multimode 100mb sfp to match the moxa switch)

All moxa switches under trouble shooting test have been upgraded to firmware 3.3 from 3.1 and 2.7

All VLAN and network settings are confirmed and running ok.

Tested all switches that were failing with duplex Auto set to having duplex Full set. Test either reversed issue (Write 93 Read 2) to (Write 2mb Read 93) or didn’t affect the test.

Tested all switches that were failing with duplex Full set to having duplex auto set. Test either reversed issue (Write 93 Read 2) to (Write 2mb Read 93) or didn’t affect the test.

Tested with a Cisco 2960 8TC using GLC-SX-MM at both locations back to the 3750x and the results proved there is no issues between two cisco swithces.  (Be aware that this is 850nm not 1300nm)

Confirmed the GLC-GE-100FX works for multimode at 1270 - 1380nm with optimal being 1300nm

Confirmed that OM3 Cable works between 850 and 1300nm with 1300 being a maximum or 500meters as Gigabit Ethernet LX


Discussion Forums and Support Forums

Mentioned the Duplex with Moxa Switches as an issue where Cisco can set the Duplex to Full, Half or Auto. Moxa are unable to set their configuration to allow a static duplex settings

This issue has been discusses on several occasions when running moxa switches with other switches like Hirschmann, HP and Cisco moxa do not work well with others.



Further testing to perform,

Downgrade Firmware in moxa and Cisco re test

Test switches with base no configuration in the switches

Test with Cisco switch in place of Moxa switch


Other Actions done

Contacted Moxa support waiting on a reply

Contacted Cisco Support waiting on a reply

Community Member

Did you find a resolution to

Did you find a resolution to these issues?  I wonder if the issues remained using the same SFP model (Cisco or Moxa) in both disparate switches.  I know Cisco requires a command to allow non-cisco SFPs to function.

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