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Aspirant

SFP/SFP+ Question (GC728X to AX6000)

Hi all,

     From what I understand, the SFP+ slots in the GC728X do not permit auto-negotiation when using an AXM765 SFP+ module.  My question is, does that limitation originate in the AXM765 module, or is it a function of the GC728X that holds true for ALL SFP+ modules?  I am fairly new to the SFP/SFP+ realm, and am a little leery about picking up a SFP+ module that says it supports multi-rate.  I recently received a Nighthawk AX6000 for testing, and I'm wondering if I can use the 5G/2.5G/1G LAN port to a SFP+ module in AP mode.  All equipment is located in our wiring closet so distance isn't a concern.

 

Thanks!

Model: GC728X| Insight Managed 28-port Smart Cloud Switches
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Guru

Re: SFP/SFP+ Question (GC728X to AX6000)

The point is that there is on neither on the fiber link nor on the SFP+ SR & LR optics - different from copper Ethernet we're so used to - no negotiation.


The GC728X Data Sheet says "• 2 x 10GBASE-X Dedicated SFP+ Fiber ports supporting 10G/1G speeds" - so if such a Multi-Gig SFP+ module doesn't work on the other speeds, nothing to complain.

 

An SFP+ port can support multiple speeds, however even Netgear's real Multi-Gig switches like the unmanaged XS505M/XS508M or the Smart Managed MS510TX show in the specs (and the data sheet) 1G/10GBASE-X SFP+. We've seen in some business grade devices that the SFP+ ports can be configured to auto negotiation resp an error message is thrown when auto-negotiation is on and a SFP+ optics module is plugged.

 

One could imagine that a Multi-Gig switch might be able to take such a module and might allow to run 2.5Gb or 5Gb and that it's simple not documented accordingly. 

 

@LaurentMa  need your backing here - aware you are not the PLM for the Smart Managed Pro/Plus switches.

 

 

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NETGEAR Expert

Re: SFP/SFP+ Question (GC728X to AX6000)

Hi @Synica1 and @schumaku 

 

OK let me explain. The AXM765 SFP+ transceiver can work at:

  • 2.5Gbps when inserted in a 2.5Gbps SFP port (garage)
  • 5Gbps when inserted in a 5Gbps SFP port (garage)
  • 10Gbps (30 meters) when inserted in a 10Gbps SFP+ port (garage)

To my knowledge, there is no such switch today with 2.5Gbps or 5Gbps SFP ports (garages). So basically, the AXM765 can only be used in a 10Gbps SFP+ port,  on a switch like the GC728X. You can connect another 10GBASE-T device (switch, or host) to the transceiver using CAT6A wiring up to 30 meters, at 10Gbps only.

 

The SFP+ port will not be capable of 2.5Gbps or 5Gbps, so AXM765 is "forcing" you to connect from a 10GBASE-T host at 10Gbps speed.

 

If you want, you can use a regular 1Gbps SFP transceiver like the AGM734. In that case, the SFP+ port will automatically revert back to 1Gbps (because it's detected as a purely 1Gbps transceiver), and you will be able to connect to your router using Cat5E or better, but at 1Gbps speed.

 

I hope this helps!

Regards,

 

 

Laurent Masia
NETGEAR Senior Product Line Manager, Managed Switches
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Aspirant

Re: SFP/SFP+ Question (GC728X to AX6000)


The SFP+ port will not be capable of 2.5Gbps or 5Gbps, so AXM765 is "forcing" you to connect from a 10GBASE-T host at 10Gbps speed.

 

If you want, you can use a regular 1Gbps SFP transceiver like the AGM734. In that case, the SFP+ port will automatically revert back to 1Gbps (because it's detected as a purely 1Gbps transceiver), and you will be able to connect to your router using Cat5E or better, but at 1Gbps speed.


Thanks for the speedy responses, @schumaku and @LaurentMa !!

 

That definitely helps explain things; to make sure I understand, it would operate in either 1Gbps or 10Gbps (in a SFP+ garage), but there's no half-duplex/multi-rate capability.  The resultant speed would be the lowest capable rate (1Gps or 10Gps) in the connection circuit.  In this case, the best solution will probably be to set up an 802.3ad connection from the switch to the two aggregate-capable ports on the AX6000, theoretically allowing for a 2Gbps rate with appropriate cabling/environment settings.  That also leaves the SFP+ garages free if I want to upgrade the NIC on our storage / client backup server.  Plus, there's still the available SFP garages if I want to add an AGM734 for our in-line firewall/security appliance solution.

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