Question I've always had about DAC (SFP Cables).

[thecomputerguy]

So in this environment we are using a Ubiquiti UDM SE with 2 available SFP ports alongside a 48-Port Ubiquiti switch with two available SFP ports. I know the correct way to connect these two devices is using a DAC cable and SFP ports as opposed to connecting them via a Cat6 cable port to port... but why?

The key points that make me ask this question is...

The clients internet is 300d/100u.
All clients are only cable of 100/1000 or are using the a standard 1G ethernet port or are on WiFi.
The connectivity speed between the UDMSE and the 48Port Switch using ethernet should be 1000mbps using an ethernet cable (right?).

What does using the SFP port with a DAC cable utilizing 10G SFP connected between the two devices bring to the table if all client connectivity maxes out at 1000mbps anyways and their internet is 300/100?

I fell kind of dumb asking this because I should know, but I don't.

 

[Sky-Knight]

SFP port is 1gbit, and no different in any way other than media type. Now, if it's an SFP+ port, you can get 10gbit and above, which gives far more bandwidth between the two devices. In the case of the setup you've described here it doesn't grant much benefit... EXCEPT in one specific case.

Unifi switches aren't layer 3... so if you're moving traffic between VLANs, it's bouncing off that UDM SE potentially saturating the link between the two devices. Generally I try to get 10gbit from the edge router, through all the core switches as a matter of convention, and extend 10gbit to any hypervisors that may be on site. You won't need all of that bandwidth, but it's nice to not have to team up several 1gbit connections to ensure maximum connectivity to and from the server.

Then again, all of this assumes there's something on the network that can USE all that connectivity. 10gbit anything on premise is losing its shine these days if you're 100% cloud based, UNLESS you have a 1gbit or faster Internet connection that is.

 

[YeOldeStonecat]

For a 300 meg link, I wouldn't lose sleep over the choice.
We mostly use the DAC cables with Unifi stacks. For a "rack"...DAC is fine. Fiber shows superiority when it comes to distance, as DAC has...I think a 15m max length.

Fiber is also more flexible...yet delicate, where as DAC is stiff, but I've never let that make things ugly, always did fine using short DAC cables to keep things neet.

 

[YeOldeStonecat]

Unifi switches aren't layer 3...

Ubiquiti has had layer 3 switches for some time...

Switch Pro 48 PoE - Ubiquiti Store

A 48-port, Layer 3 PoE switch.

store.ui.com

Yes..many years ago, their early layer 3 switches had some limitations which gathered anti-Unifi curses from the Cisco snobs looking down upon UI, but they've (UI) been improving and getting legit.

 

[Sky-Knight]

Ubiquiti has had layer 3 switches for some time...

Switch Pro 48 PoE - Ubiquiti Store

A 48-port, Layer 3 PoE switch.

store.ui.com

Yes..many years ago, their early layer 3 switches had some limitations which gathered anti-Unifi curses from the Cisco snobs looking down upon UI, but they've (UI) been improving and getting legit.

They can get legit all the want, until they solve the supply issues so we can get crap from distribution reliably... my outfit will never sell them.

Which is kind of sad, I like what Ubiquiti is trying to do. But right now it seems they're killing the channel for direct sales to get margin.

 

[YeOldeStonecat]

They can get legit all the want, until they solve the supply issues so we can get crap from distribution reliably... my outfit will never sell them.

Which is kind of sad, I like what Ubiquiti is trying to do. But right now it seems they're killing the channel for direct sales to get margin.

Supply issue was solved quite a while ago, every brand had the issue in covid. My colleague does some Fortinets....he had lead times of freaking 8-9 months at one point! Similar with some HP/Arubas. We've kept stock of UI products just find during the past..at least 2 years.

 

[Sky-Knight]

Supply issue was solved quite a while ago, every brand had the issue in covid. My colleague does some Fortinets....he had lead times of freaking 8-9 months at one point! Similar with some HP/Arubas. We've kept stock of UI products just find during the past..at least 2 years.

So you have often reported, and yet when we need Unifi year it's 3-4 months out STILL.

Heaven help me if I need a bloody cloud key, serious crap shoot. We've abandoned Unifi entirely in favor of Aruba Instant On, because we order those, and they show up on time. We have zero interest in holding stock to make things up, I'll just sell something from a company that knows how to warehouse things.

WAPs? No problem on those, can get what we need. Cloudkeys are a crap shoot. Switches are a crap shoot.

 

[YeOldeStonecat]

Dunno where you're shopping....switches have been abundant for us for quite a while from many different resources, as well as gateways. Cloudkeys are yesteryear, an old approach they no longer do, they're either built into the gateways like the Dream Machine Pros, or...like most MSPs do, you use a multi tenant cloud controller (such as roll your own, or Hostifi, or Ubiquiti's own service).

Having business clients, we'd never "not have stock on the shelf". Regardless of brand, if a client tanks a switch or edge device, we're not going have the client wait for us to order a replacement and run out to install it in a day or three...we have to replace it "right now". So yeah, we always stock lots of extra firewalls/switches/APs/p2p radios/etc. Of all sizes 'n models. Failure to do that is not doing justice to the clients.

 

[phaZed]

I have not had any stock issues with Unifi since 2nd or 3rd quarter last year... but it was a mess in 2022-1Q23 - seems pretty much stabilized now though.

 

[NETWizz]

So in this environment we are using a Ubiquiti UDM SE with 2 available SFP ports alongside a 48-Port Ubiquiti switch with two available SFP ports. I know the correct way to connect these two devices is using a DAC cable and SFP ports as opposed to connecting them via a Cat6 cable port to port... but why?

The key points that make me ask this question is...

The clients internet is 300d/100u.
All clients are only cable of 100/1000 or are using the a standard 1G ethernet port or are on WiFi.
The connectivity speed between the UDMSE and the 48Port Switch using ethernet should be 1000mbps using an ethernet cable (right?).

What does using the SFP port with a DAC cable utilizing 10G SFP connected between the two devices bring to the table if all client connectivity maxes out at 1000mbps anyways and their internet is 300/100?

I fell kind of dumb asking this because I should know, but I don't.

It mainly matters for devices that do stacking. Many of them require some form of stacking cables like the DAC, QSFP+ DAC, or StackWise 480, StackWise 1T etc.

Otherwise they just save ports. For example I always buy 48 port patch panels and 48 port switches… I NEVER uplink a Cisco Catalyst 9300x-48hx for example with a built-in copper port. I will insert a copper SFP just to keep it clean… and to prevent someone unplugging stuff

 

[NETWizz]

SFP port is 1gbit, and no different in any way other than media type. Now, if it's an SFP+ port, you can get 10gbit and above, which gives far more bandwidth between the two devices. In the case of the setup you've described here it doesn't grant much benefit... EXCEPT in one specific case.

Unifi switches aren't layer 3... so if you're moving traffic between VLANs, it's bouncing off that UDM SE potentially saturating the link between the two devices. Generally I try to get 10gbit from the edge router, through all the core switches as a matter of convention, and extend 10gbit to any hypervisors that may be on site. You won't need all of that bandwidth, but it's nice to not have to team up several 1gbit connections to ensure maximum connectivity to and from the server.

Then again, all of this assumes there's something on the network that can USE all that connectivity. 10gbit anything on premise is losing its shine these days if you're 100% cloud based, UNLESS you have a 1gbit or faster Internet connection that is.

SFP+ is 10 Gbps and backwards compatible to SFP. It is NOT “above” 10 Gbps

SFP28 is 25 Gbps, and backwards compatible to SFP/SFP+

SFP56 does 50 Gbps and is backwards compatible but not always all the way back to SFP

SFP-DD does 100 Gbps and is backwards compatible …

 

[HCHTech]

Don't forget also that the SFP modules are switch/vendor-specific. Whenever I need one of these (not often, but it happens) I've used fs.com and just do a support chat with them saying I need to connect e.g. a Mellanox 4xSFP228 card to a Unifi switch. They build the cable and it just works. If I did this every day like @NETWizz , I'm sure I'd know which modules were compatible with which NICS and which switches, but I don't, so I don't. The folks at fs.com DO know and they don't want returns, so they just figure it out for me.

 

[NETWizz]

Don't forget also that the SFP modules are switch/vendor-specific. Whenever I need one of these (not often, but it happens) I've used fs.com and just do a support chat with them saying I need to connect e.g. a Mellanox 4xSFP228 card to a Unifi switch. They build the cable and it just works. If I did this every day like @NETWizz , I'm sure I'd know which modules were compatible with which NICS and which switches, but I don't, so I don't. The folks at fs.com DO know and they don't want returns, so they just figure it out for me.

That makes sense. I have heard great things about FS.

That said, I personally buy all Genuine SFP, SFP+, etc. because I am too busy to deal with any shenanigans. That said, I still sometimes have problems.

Just looking through the list of opened transceivers, these are from our box. Everything to the right of the Blue cable is Brocade/Ruckus... Mostly SX, some SR, and a little LX. Also some TX for copper. Cisco is to the left of the blue 1' network cable, and all are genuine.

I have some new inventory, too.

 

[HCHTech]

That is a lot of $$ in transceivers!! Yikes.

 

[YeOldeStonecat]

Don't forget also that the SFP modules are switch/vendor-specific. Whenever I need one of these (not often, but it happens) I've used fs.com and just do a support chat with them saying I need to connect e.g. a Mellanox 4xSFP228 card to a Unifi switch. They build the cable and it just works. If I did this every day like @NETWizz , I'm sure I'd know which modules were compatible with which NICS and which switches, but I don't, so I don't. The folks at fs.com DO know and they don't want returns, so they just figure it out for me.

We used to use FS.COM ....she had the Brocade modules which worked great in Unifi switches...since the switches were basically Brocade hardware. But we started just getting the Unifi sets when UIs prices came way down......boxes of the the fiber modules (usually had at least a few dozen)...and keep around a dozen of the various length DAC cables.

 

[NETWizz]

We used to use FS.COM ....she had the Brocade modules which worked great in Unifi switches...since the switches were basically Brocade hardware. But we started just getting the Unifi sets when UIs prices came way down......boxes of the the fiber modules (usually had at least a few dozen)...and keep around a dozen of the various length DAC cables.

DAC cables are great for stacking with most vendors.

Here are the Brocade DAC cables we still have from 2017 despite removing Brocade and installing Cisco... pretty much obsolete stuff:

 

[YeOldeStonecat]

Yeah those boxes look familiar.
Used to have a bit for HP too. (now Aruba)