SFP cable for ER4 to EdgeSwitch 24 Lite

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fe31nz

1230 posts

Uber Geek

#281552 25-Feb-2021 00:16

I have an EdgeRouter ER4 as my router and an EdgeSwitch 24 Lite as my main switch. I would like to be able to use one more port on my ER4 to connect to my old switch to use it as a testing network, isolated from my normal network. The ER4 has ETH0 as the WLAN port, ETH1 as my "Outer" (DMZ) network and ETH2 as my main network ("Inner"), with both ETH1 and ETH2 connecting to the ES24. The ER4 also has an unused SFP port as ETH3. I looked at getting an SFP to Ethernet adapter to connect the new network to ETH3, but they are very expensive (>$100). As an alternative, I could get an SFP to SFP cable and use that to replace one of the ETH2 or ETH3 cables to the ES24, freeing up a copper ETH port on the ER4. SFP to SFP cables, however, seem to be few and far between in NZ. The cheapest cable I could find for this job is actually SFP+ to SFP+:

https://www.gowifi.co.nz/cabling/uc-dac-sfp.html

But as I have no experience at all with SFP/SFP+, I do not know if an SFP+ adapter will negotiate down to SFP at both ends and work correctly. So does anyone have any experience with this? Or is there some other way of doing what I want that I have missed?

OzoneNZ

102 posts

Master Geek

ID Verified

#2662414 25-Feb-2021 00:48

FiberStore is the go-to for most people purchasing SFP/SFP+ gear without paying ridiculous OEM prices

I think a pair of these SFP transceivers is what you're after: https://www.fs.com/products/20057.html

At $28 NZD a pop it will give you a regular RJ45 socket, then you can just use a CAT5e/CAT6 cable between the two ends

Like you said the DAC cable you linked is SFP+, which won't work in SFP ports. There are SFP DAC cables but I think RJ45 in this case is just going to be easier, plus the distance you can run over CAT5e/CAT6 is far greater than what DAC cables can do.

Should also note that (most?) SFP/SFP+ gear does not auto-negotiate in my experience, not a big deal, just requires setting the link speed on both ends manually to 1000 Mbit full-duplex in your case.

Little nit-pick, "Ethernet" is a protocol rather than a connector - SFP/SFP+ ports also carry Ethernet :)

fearandloathing

503 posts

Ultimate Geek

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Lifetime subscriber

#2662428 25-Feb-2021 07:06

I use the previously mentioned https://www.gowifi.co.nz/cabling/uc-dac-sfp.html to go between a er4 and a USW-16-POE

cyril7

9058 posts

Uber Geek

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#2662429 25-Feb-2021 07:21

Hi an sfp+ cable between a sfp+ and sfp port will work just fine.

Cyril

Tinkerisk

4227 posts

Uber Geek

#2662554 25-Feb-2021 09:29

Universal DAC+ will work for 1GbE/s when configured in switch setup manually since it doesn't do auto-negotiation.

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fe31nz

1230 posts

Uber Geek

#2662833 25-Feb-2021 23:48

Thanks everyone. I have decided to go with a couple of SFP to RJ45 transceivers from fs.com. That way I get full flexibility, at a not too unreasonable price. DHL says arriving on the 4th.