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Using SFP+ modules in switches that are only SFP capable?

AssetBurned
Tutor

Using SFP+ modules in switches that are only SFP capable?

Hi,

 

So what happens if I pop in an SFP+ module into a switch that can only handle SFP?

 

From what I read up so far is that SFP+ modules generally should also work in SFP ports, but does someone tried it out on any Netgear switch particular on the GS110TPv2 or GS724TS ?

 

I mean there are several options that I could think of right away.

1) as most mudules do not support autonagotiation and fallback to lower speeds, it would be just the throughput that get reduced but it is still an e.g. 10G connection.

2) the module just refuses to work at all

3) if the module supports different speeds, then the higher tier wouldn't be available

 

CU AssetBurned

Model: GS110TPv2|ProSafe 8 ports gigabit PoE smarta switch, GS724TS|ProSafe Gigabit Stackable Smart switch|EOL
Message 1 of 8

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schumaku
Guru

Re: Using SFP+ modules in switches that are only SFP capable?

The counterpart was always a 10GBase-T resp, 1000MBase-T switch port.

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Message 7 of 8

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schumaku
Guru

Re: Using SFP+ modules in switches that are only SFP capable?

Tell us exactly what configuration ideas you have in mind.

 

Be aware the fiber links _never_ use any auto negotiation. 

 

A Multi-gig capable 10GBase-T SFP+ would run at 10 Gbit/s on a 10 G SFP+ slot, at 5 Gbit/s in a 5 Gbit/s slot, ... 

Message 2 of 8
AssetBurned
Tutor

Re: Using SFP+ modules in switches that are only SFP capable?

It is more a general question than an practical usecase that I plan to implement.

 

So from my understanding it is comparable to connecting an 1000Base-T Ethernet adapter to an old USB 2.0 port. The adapter and the connection will still be a gigabit connection, but the bottleneck is the USB2.0 connection. The device that has the USB port would only get the max throuput of whatever USB would give it.

 

So if I have a connection with SFP+ module for 10G fiber in an SFP slot on one side of the cable. The connection would be still OK, but since that side only supports slower speeds the whole throughput would be limited to 5G as this is the max for the SFP port?

 

Regarding the autonegotiation.

Well there seems to be modules that can do different rates (maybe selectable by the switch firmware). https://www.intel.com/content/dam/doc/product-brief/ethernet-sfp-optics-brief.pdf also listed as dual rate at http://www.intel.com/support/network/adapter/pro100/sb/CS-030612.htm within "What are the SFP+ and SFP module requirements for the Intel® Ethernet Converged Network Adapter X520 Series?"

And than there are also those cables that support Cat 6 Ethernet cables that can do it, but those wouldn't be optical.

Message 3 of 8
schumaku
Guru

Re: Using SFP+ modules in switches that are only SFP capable?

Afraid, I don't think an SFP+ module is supposed to be operational in an SFP slot in general. From some tests with "no-name" but Multi-Gig capable 10GBase-T SFP+ modules, we find that 

 

- SFP+ module plugged to an SFP port (tried several Netgear Smart Managed Plus or Smart Managed Pro models) will be powered, 

-- a link to a 10G switch will come up at 10G, but the SFP "interface" on the switch will stay down, no LED activity.
-- a link to a 1G switch will come up at 1G, but the SFP "interface" on the switch will stay down, no LED activity.

- SFP+ module plugged to an SFP+ 10G capable switch
-- a link to a 10G switch will come up at 10G, SFP+ "interface" on the switch comes up, LED on, connectivity OK

-- a link to a Multi-Gig switch (tried 2.5G port, 5G port) will come up at the link rate of the per, SFP+ "interface" on the switch comes up (says 10G), LED on, connectivity not OK.

-- a link to a GbE switch will come up at the link rate of the per, SFP+ "interface" on the switch comes up (says 10G), LED on, connectivity not OK.


The point on the Intel document is this: "• Supports rate selectable 1.25 Gb/s or 9.95 to 10.3 Gb/s bit rates" for the fiber SFP+ modules mentioned. There are ways to control/set the speed - there is however no auto speed negotiation on the SFP interface level. For the majority of switch SFP/SFP+ deployments, we need the standard "fastest" rate - being as an interconnection, or to connect some servers.

Message 4 of 8
schumaku
Guru

Re: Using SFP+ modules in switches that are only SFP capable?

To add some confusion:

 

- SFP+ module plugged to an SFP+ 10G capable switch (MS510TX)
-- a link to a 10G switch will come up at 10G, SFP+ "interface" on the switch comes up, LED on, connectivity OK (as expected)

-- a link to a GbE switch will come up at the link rate of the per, SFP+ "interface" on the switch comes up (says 10G), LED on, connectivity  OK.

Message 5 of 8
AssetBurned
Tutor

Re: Using SFP+ modules in switches that are only SFP capable?

On the GbE side, was that an 10g or 1g module in an SFP port?

Message 6 of 8
schumaku
Guru

Re: Using SFP+ modules in switches that are only SFP capable?

The counterpart was always a 10GBase-T resp, 1000MBase-T switch port.

Message 7 of 8
AssetBurned
Tutor

Re: Using SFP+ modules in switches that are only SFP capable?

Great that is what I was expecting/hoping to read.

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