Will a 10GBe DAC (H10GB-CU3M) work in a 1GB SFP port?

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marteng

New Member
Jul 9, 2013
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Hello,

I'm using a Netgear M5300-28G3 switch and have a spare 10GBe port at a server (Intel X520-DA2) and a spare 3m SFP+ DAC cable (Cisco H10GB-CU3M).

Question: will the DAC cable work in a 1GBe SFP port of the switch? (all 10GBe ports are already in use).

Alternatively I have 2x 10GBe SFP+ modules (Finisair FTLX8571D3BCL originally from the Intel X520-DA2) and a LC-LC optical cable. Will this SFP+ module work in the SFP ports of the switch?

Thank you for your help.

Bye,
Martin
 
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Dev_Mgr

Active Member
Sep 20, 2014
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Generally the transceiver itself is singular speed only.

So a 10Gbit DAC cable, or 10Gbit optical transceiver won't work in a 1Gbit port.

It also means that you cannot have a 1Gbit optical transceiver on one end, 10Gbit transceiver on the other end and expect them to connect.

Nor can you force a 10Gbit DAC or transceiver to go down to 1Gbit speeds.

I'm not sure if 1Gbit DAC cables exist (don't think I've ever seen one), so you may have to get two 1Gbit optical transceivers and an optical cable to connect an SPF port to an SFP or SFP+ port.
 

Evan

Well-Known Member
Jan 6, 2016
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I can confirm those Cisco cables won’t work at 1G between 2 cisco switches (I tired one day since I had one in hand instead of leaving the DC I was in to source the required SFP and cable, was interested to know)
They should only be 10G

Never seen a 1G DAC, just 10G, 40G, etc
 

spali

Member
Nov 4, 2018
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I think Cisco does some magic sometimes... i.e. have two SMB SG500 stacked with SFP-H10GB-CU1M (same, just shorter). They stack at 5GBbit.
Never tried without stacking, but as I read, it should then work at 1Gbit. At least on this switches.
I will have a similar problem soon. I will get a new core switch and have to uplink the SG500 switches to a SFP+ 10Gbit switch. I will at least try the same cables.