Comments on: MikroTik CRS518-16XS-2XQ-RM 25GbE and 100GbE Switch Launched

By: Dreamslacker

Dreamslacker — Tue, 19 Jul 2022 14:15:25 +0000

@Bob H
Yes, it will. From the product brochure: “The 25-gigabit ports are backward compatible with 10 Gigabit and 1 Gigabit SFP devices. Mix and match as you need!”

In general on most devices, a SFP28 port will be capable of running at 10Gbase-X as well. Think of SFP28 as being SFP+ but with higher clock rates capability.
Ultimately this also boils down to firmware and transceivers supporting this. E.g. Some 10GBase-SR transceivers could only run at 10GbE but others could support 1GBase-SX as well.
Also, on some switches, they could not run 1GBase-X on SFP28 ports due to firmware limits but this is typically on switches designed for DC ToR or aggregation.
In some cases, this proves to be a major annoyance when you need to add a small amount of client devices running 1GbE and end up effectively needing another (set of) switch(es) just to cater for this.
Most notably, I’ve had to design and implement perimeter/ DMZ networks for AREN and supercomputers with varying WAN link types (mostly 100G, some 10G, and a very select few 1Gbase-T hand-offs) and had to have different border-leaf/ WAN switches just to cater the 1Gbase-T hand-offs.

By: Sean

Sean — Tue, 19 Jul 2022 12:42:41 +0000

I am running CRS312, CRS309 and CRS305. All on ROSv7.3 stable. No stability problems. If you are migrating from old settings, just wipe all, reset, reconfigure from scratch, reboot. Just do it over CLI, all done in minutes.

By: Bob H

Bob H — Mon, 18 Jul 2022 20:38:02 +0000

One thing I wasn’t sure about is if the SFP28s will negotiate down to 10G for legacy applications. The SFP28 NICs I have do that, but I imagine there’s some requirement for it to be intentionally implemented.

By: Andis

Andis — Mon, 18 Jul 2022 07:24:52 +0000

Of course, you couldn’t use any random four ports, only specific group of 4 adjacent ports.
Q in QSFP means “four”, as there are 4 parallel tx/rx channels, while SFP has only one. QSFP literally is for SFP ports in a single connector.

By: Andis

Andis — Mon, 18 Jul 2022 07:14:31 +0000

@Malvineous i think – yes. If switch chip configuration allows it, then there would be no problems with that. But question is, does it ? And does SW allow it.

@Cody Weaver – i guess he wants to convert this switch to 6 port 100G qsfp28 switch.

By: Cody Weaver

Cody Weaver — Sun, 17 Jul 2022 15:39:58 +0000

@Malvineous I’ve heard this ask before, but couldn’t ever find a proper use case. Without bonding, you’re going to need a NIC capable of negotiating with the switch at L1 level to bond the multiple links. If you’re already getting a NIC that can negotiate with the switch, then why do you even need to do multiple, bonded connections? Even 100G is possible on a single MMF LC fiber using BiDi transceivers over OM3 if your distances are less than 75m.

The only use case I can think of is that for some reason you have 25Gb NICs you are unwilling to replace in your servers, somehow have 4 ports, and don’t want to connect them to the primary 25G ports.

If there’s another use case, I’d be curious to hear it, but in most reverse scenarios, I think we have optics now that account for nearly every use case.