NEW THREAD: 10G SFP+ Auto-Negotiating to 1G?

[visitor68]

• Can a 10G SFP+ SR optic plugged into switch "A" AUTO-NEGOTIATE to 1G to support a 1G SFP SR optic plugged into switch "B" at the other end of the fiber cable?
• In short, what I am asking is whether a 10G SFP+ optic (SR/LR - doesn't matter) can be connected with fiber (of course) to a 1G optic and negotiate DOWN?
• If not, how do I connect that 1G sfp+ optic to a 10G sfp+ switch port?

NOTE: I know Cisco SFP+ optics only operate at 10G and Cisco SFP optics operate only at 1G. But my question is a general question about SFP/SFP+. From my understanding, SFP+ CANNOT (regardless of vendor) negotiate down to 1G because the SFP+ standard defines a speed range between 4.25 Gbps to 16Gbps. Can someone verify?

[Leo Laohoo]

Move this thread to Optical Networking section so Marvin and Tom can put their comments in.

[Marvin Rhoads · Accepted solution]

Optical transceivers do not autonegotiate. It doesn't matter if they're from Cisco or Transceivers 'r Us. 

The optics are driven by ASICs that are fixed speed. A very few models have dual speed 100 Mbps and 1 Gbps but those are quite unusual and the vendor builds in two wavelength VCSELs to accomplish that. I'm not seen any such offering for 1 Gbps and 10 Gbps. 

Many SFP+ 10 Gbps ports are capable of accepting 1Gbps SFPs. Share your model and software revision and we can point you to the relevant compatibility matrix citation. 

[visitor68]

Marvin, thanks for the feedback. Been away so sorry for the delay. I dont want to get into specific model numbers, etc. I am more interested in general theory. Can I plug an SFP optic into an SFP+ port so that I can connect that optic to a 1G SFP optic on the other end? Im asking because I have a 10G switch but have to accommodate  a handful of 1G optical connections from a 1G switch

[Marvin Rhoads · Accepted solution]

In general theory, they will fit and you can plug them in.

General theory doesn't help because the compatibility of a given transceiver in a given port depends on a combination of the firmware embedded on the ASIC inside the transceiver with the IOS running on the particular hardware you are plugging into.

So sometimes it will work and sometimes it will not. If it doesn't, you've made an expensive mistake that could be easily avoided by first consulting the compatibility matrix.

[Reuben Farrelly]

Here is one common Optic SFP that does do both 1G and 10G:

Intel E10GSFPSR and

Intel E10GSFPLR

http://www.intel.com/content/dam/doc/product-brief/ethernet-sfp-optics-brief.pdf

http://www.intel.com/support/network/adapter/pro100/sb/CS-030612.htm (expand section 1)

I know for certain that they do support both 1G and 10G as for quite a while I ran these SFPs with Cisco GLC-SX-MMD, and eventually (now) Cisco SFP-10G-SRs.  No config changes or modifications were required to support this functionality.

This was in a UCS server with a supported Cisco UCS Intel X520 card.

[Marvin Rhoads]

Thanks Reuben,

I hadn't seen that offering before.

I see they have to use the Intel X520 card - I wonder how the optics actually work inside (dual set or are they actually changing the modulation speed on a single optic). There must be something special in the driver for that card that does the trick.

[aymen.mami]

Thank you Reuben,

You're a life saviour.

I have Cisco C220 M4 server and i have to connect it to Monomode 1 Gbps network (hosting a virtual CSR).

So the Cisco UCS Intel X520 card will save the day :)

Do you know if those Adapter comes with SFP included? Did you purchase them from Cisco?