
Realtek 2.5 GbE PCIe Cards Now for Sale - DiabloD3
https://www.anandtech.com/show/15026/25-gbe-card-w-realtek-rtl8125-makes-a-debut
======
angry_octet
For those confused as to why this exists, it's about cabling. It simply isn't
possible to run 10Gbase-T over most existing structured cabling. Even with new
cabling the network closet is often too far away. But 2.5GbE works in many
situations.

If you're doing new cabling go multimode OM4 fiber. It isn't that expensive
(buy factory terminated, use MTP trunk patching) and it supports stupendous
data rates.

~~~
Ao7bei3s
Yes, for "just above 1G, and must reuse existing copper wiring, and both sides
take PCIE", the card from the article will do. But it's a pretty narrow use
case.

I agree with the notion of using fiber. I would certainly stay away from
hardwired copper NIC's for anything except 1G, especially rarity ones like the
one in the article. Rather, get 10G NIC's with SFP+ cages. Doesn't have to be
a pricey Intel card, the cheap Melanox ones are acceptable for most users.

I disagree about OM4. If you're doing new fiber runs, singlemode (OS2 fiber)
is the way to go. It's not really expensive anymore. But yeah, OM4 rather than
OM3 for all fiber runs (for back to back patches, it doesn't matter ofc).

(Also, since we're talking about fiber networks... my personal lessons learned
are: buy reflashable transceivers, especially when that's the difference
between having DDM (Digital Diagnostic Monitoring) on all long runs and
running it blindly. Standardize on a connector, hopefully LC. Be consistent
which side TX and which is RX. Keep a 100-pack of dust caps around. And clean
your fibers before inserting, especially patch fibers that get thrown around
(they can look pretty bad on the fiberscope). Don't bother with Direct Attach
Cables. Stay away from NICs with fixed 10G-Cu ports. Visual fault locators are
cheap. BiDi SFP's are wonderful in one-fiber-run-broke or need-another-link-
now type emergencies, so keep a few in reserve. And lastly, since all of this
costs money, it's easier to beg for reimbursement than to ask for a purchase
order.)

~~~
angry_octet
Hmm, lots more transceivers support multimode (not just Ethernet, serial/video
etc) and a lot cheaper too. Direct attach is the only way to go for in-rack,
both cost and cooling effects. Probably not the best in an office environment
though.

In the desktop, QNAP recently released 8/12 port SFP+/T switches starting at
US$500, which is the sort of pricing that will push this tech into small
business. Probably buggy as hell at saturation and no features, but who cares,
these are for doing occasional file transfers instead of passing around USB3
SSD drives.

[https://nascompares.com/2018/04/12/unboxing-the-
qsw-1208-8c-...](https://nascompares.com/2018/04/12/unboxing-the-
qsw-1208-8c-qnap-10gbe-switch-its-finally-here/)

~~~
Ao7bei3s
I agree MM is more widespread, but I thought we were talking about new cabling
(and I took that to include the transceivers). (Serial over fiber? Nice,
didn't know that existed.)

Pricing-wise, what I meant is:

$18: 10G-SR (MM):
[https://www.fs.com/products/11552.html](https://www.fs.com/products/11552.html)

$24: 10G-LR (SM):
[https://www.fs.com/products/11555.html](https://www.fs.com/products/11555.html)

Compared to the cost of actually running the fiber through the building,
that's not too bad for trunks. As I said, I don't mind multi-mode for the last
hop, which is where price is a larger concern due to quantity. And in
organizations where OEM pricing is used as baseline, relative to that a
resourceful admin can go to single mode and still come out ahead (it's not a
fair comparison, but reality in some places). Sure, things are probably
different in an actual DC.

Direct attach is certainly cheaper (at first), but it can be a hassle compat
wise, and I've never had quite the right length available. I can't speak to
cooling, that's never been my department.

~~~
angry_octet
Wow those SR SFP prices have fallen.

Every SFP adds about 1W, but 10Gb-T ports are particularly thirsty, they were
5W when first introduced, still in that ballpark. It all adds up.

Another reason to prefer fiber/DA is 10Gb-T has shit latency, it has a modem
doing QAM, hence the power consumption. Probably only relevant for HPC or HFT,
but just inelegant.

------
nodesocket
Seems very limited if you can't get any switches that support 2.5GbE. Makes
more sent to just go the full 10GbE route, though 10GbE switches are still
very expensive.

Anybody recommend a better option than the Ubiquiti ES‑16‑XG[1]. Unfortunately
most of the ports are SPF+ with only 4 ports being RJ45 10GBASE-T.

[1]
[https://www.ui.com/edgemax/edgeswitch-16-xg/](https://www.ui.com/edgemax/edgeswitch-16-xg/)

~~~
bch
IIUC, the 2.5Gbase-t will work w cat5e cables, which is the highest signalling
(or lowest cable spec) to fulfill building out a network. If you’re stuck w or
otherwise committed to Cat5e, 10GbE isn’t an option. I guess it’d be a case-
by-case decision whether that’s a blocking consideration...

~~~
xenadu02
In practice a lot of Cat5e cabling can support 10Gbe up to ~40m.

I guess the standards folks are hoping future equipment just supports 2.5Gb,
5Gb, and 10Gb then auto-detects the link quality and scales to whatever the
cabling can support.

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algaeontoast
It’s really odd to me that 2.5G was seen as the next logical consumer step
forward in Ethernet tech. Especially since “consumer” grade 10G cards have
been available for some time.

Granted, I’m a bit out of the consumer use case for this stuff since I’ve
transitioned my home to 10G fiber (in many cases easier to run and cheaper
than 10G copper Ethernet cable).

~~~
kondro
This is more about cabling capabilities than the NICs. 2.5Gbe can run on
Cat5e.

------
xellisx
Isnt there a 5 Gb standard too?

~~~
kbumsik
Yup, we have 5GBASE-T too.

~~~
colejohnson66
Not to be confused with 10BASE5[0] which is not to be confused with 10BASE2[1]

[0]:
[https://en.wikipedia.org/wiki/10BASE5](https://en.wikipedia.org/wiki/10BASE5)

[1]:
[https://en.wikipedia.org/wiki/10BASE2](https://en.wikipedia.org/wiki/10BASE2)

~~~
xellisx
Back in my Windows 3.11 days, 10 Base 2 on 3Com cards was the cheap solution.

