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Posts: 21
Registered: ‎07-05-2016
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Connecting two BCM53286 switches together using SERDES via fiber SFP Optical Modules

Hi,

We have a new multi-port board design which uses the BCM53286 Switch and which utilises two of the SERDES interfaces to create a dual-redundant uplink over fiber via an optical SFP module for each uplink channel. These uplink channels then normally connect to a remote router / switch, via another SFP, configured for link aggregation operation (See Figure 1 in attached document - please note that for clarity, only one of the uplink channels has been shown).

The system works fine, as do the rest of the system switches (24 x FE and 2 x GbE via a BCM5428S GPHY) and all switched ports operate as expected, along with the dual-redundant uplink. So all good there.

However, we want to configure the boards in a way that they were never intended to operate (for in-house testing purposes only) - we want connect together two of our boards together via their optical fiber uplink channels (see Figure 2 in attached document).

When we try to do this we get no link. We know that our system works fine over fibre as we have had our network connected to our board through a router and that was all ok.

However, we CAN make the boards work together if we first establish a link over fiber from one board to the router / switch (as per Figure 1), then disconnect the fiber optic cable from the remote router / switch SFP module and connect it to the second switch board SFP module (as per Figure 2) - the system then works as expected and we can pass data from one board to the next, so there can't be much wrong with this concept.

Agreed, we will never use our system in this configuration under normal circumstances, but it will drastically simplify our in-house testing if we can get this working.

Any ideas what we might be doing wrong?

Regards,

Darren

Broadcom
Posts: 300
Registered: ‎02-15-2016

Re: Connecting two BCM53286 switches together using SERDES via fiber SFP Optical Modules

Hi Darren,

By consult with our 5328x AE Vaison, please follow the register setting as below for SFP optical connection.

For Serdes SFP optical connection,   Set  Serdes/SGMII PHY reg   in Datasheet:   set  SerDes/SGMII Control 1 Register (Page B9h-BCh: Address 20h-21h, Block0)   bit4=0, bit0=1 to connect SFP for BCM53286 Serdes/SGMII ports. Thanks!

Thanks,

Ryan

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