QNAP 10gb switch, 2.5gb?

Ive been running a QNAP QSW-M408S 1gb/10gb switch for a little while now. it has 4 10gb SFP ports. I have a couple devices with 10gb cards connected to the switch over copper. I was running an RPI4 with Openwrt as a router but I decided to switch to an Odroid H2 with a netcard. The netcard adds 4 2.5gb ethernet ports. I just bumped my internet up to a 1gb connection and switched to a Netgear modem with a 2.5gb ethernet port. So the Odroid router WAN is connected to the Modem @ 2.5gb and the Odroid’s LAN port is in question.

I guess I was under the impression that I could connect the 2.5gb LAN port to the switch’s 10gb SFP port with an RJ45 transceiver. The switch doesn’t seem to be able to negotiate 2.5gb. It did however connect but I think the switch was a bit confused. I ran Iperf3 from my desktop @10gb and got 140mb up and down to the router. moving to a 1gb rj45 port on the switch gets me back to 1gb.

I’m trying to figure out if 2.5gb is just not possible with this switch or if a different transceiver will get me there. I realize there’s currently not much benefit to connecting @ 2.5gb w/1gb internet speeds but looking to do a bit of future proofing. I suppose aggregating some of the ports would probably be beneficial otherwise.

Try a different transceiver. Some of the cheap ones have problems stepping down to multigig speeds.

STH did a roundup on transceivers a while ago which might be helpful.


Thanks for the link. I have a couple of the 6Com that’s not not supported according to the article, and I have 1 GWfiber that isn’t mentioned. I’ll return that last one and try a Wiitek, it’s only 5 bucks more.

This is good to know if I ever dip my toes into SFP transceivers.

I will re-watch that video from Patrick as I do remember him mentioning some weirdness like this.

News to me that SFP+ supports 2.5 or 5gb at all tbh.

There’s all kinds of SFP+ transceivers out there these days - 10years ago you could only get 10GBase-T for copper and it was super expensive.

Most modern 10Gbase-T / RJ45 SFP+ transceivers will also do NBase-T for 2.5/5G . Some will do longer distance than 100m over UTP depending on cabling and what’s on the other end.

There’s also SFP/SFP+ transceivers with an SC connector that can be GPON provisioned.

Overall, it’s usually cheaper to get a 10G (or NBase-T) RJ45 switch if you need lots of 10G RJ45 ports. Also, you get a guaranteed 100m of distance with cat6a cabling, whereas you get less with SFP+ (fiber requires less power so and SFP+ is originally intended for fiber, and 1.5W it can provide is usually not enough to drive 10G over 100m over cat6a)

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