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RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Sun Sep 19, 2021 9:24 am

Dear all

I just bought RB4011iGS+RM and i notes that the device has SFP+ ports and i have Cisco SG300-28P 28-Port Gigabit PoE Managed Switch

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Now can i connect RB4011iGS+RM to the Router via SFP to RJ45 Copper and configure SFP+ ports as WAN in and connect ether1 as local to the Cisco SG300-28P 28-Port Gigabit PoE Managed Switch to let RB4011iGS+RM get power from Cisco switch PoE?
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Sun Sep 19, 2021 11:43 am

Answer to Q1: SFP to RJ45 Copper
Not every SFP/SFP+ Module is compatible.
If you already have one, just plug it in and see if it works.
Note: You may need to deactivate "auto-negotiate" on the sfp-sfpplus1
interface and manually select "Speed 1Gbps"

Answer to Q2: SFP+ ports as WAN
It's a mikrotik router , so of course you can configure any Port as WAN =)

Answer to Q3: ether1 power from Cisco switch PoE
The RB4011iGS+RM doesn't support IEEE 802.3XX PoE
It only supports Passive PoE with an input Voltage between 18-57 V

If you connect it, it probably won't work
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Sun Sep 19, 2021 1:21 pm

Answer to Q3: ether1 power from Cisco switch PoE
The RB4011iGS+RM doesn't support IEEE 802.3XX PoE
It only supports Passive PoE with an input Voltage between 18-57 V

If you connect it, it probably won't work

But it might. @normis explained in one post that RB4011 does negotiate 802.3 af/at PoE on its PoE-in port. The reason RB4011 is not officially declared as 802.3 af/at capable is that full rated power consumption (18W without attachments / 33W with attachments) slightly exceeds 802.3 af (15W) and/or 802.3 at (30W) limits. If your Cisco switch is 802.3at compliant, then your RB4011 will likely run just fine.

Not using that SFP RJ45 module but rather using any of existing RJ45 ports for WAN (as explained, it is possible to use any port as WAN) will shave off a few Watts from power consumption, SFP RJ45 modules are notorious for relatively high power consumption (and heat generation).
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Tue Sep 21, 2021 3:39 pm

We have several RB4011 supplied by eth1/802.3at from switches of different brands (Cisco, HPE, Zyxel and others) without any problems. According to the switch logs, the RB4011 properly negotiates af/at on eth1, although not specified.
In our experience, the power consumption of a RB4011 with 4 or less ethernet ports in use and a 1GBit SFP copper module stays between 7W and 12W (depending on CPU load) and works reliable also when supplied from an 802.3af only 15W switch port.

If you use all Ethernet ports and especially with 10GBit SFP+ copper modules, it will go up to 18W. This is slightly above the at limit of 15W, but most switches also tolerate 18W load on a af port.

Another possibility to safe power is to use a DAC cable instead of Copper SFP to connect the RB4011 to your Cisco switch. The RB4011 is specified not to support DAC cables, but for short distances it works. We have 2 devices connected to Cisco switches using this 0.5m DAC cable:
https://www.fs.com/uk/products/40109.ht ... &id=222988
Both working without problems.
But its only working for short distances. With the 1m version of the cable above, the connection gets unreliable, with the 2m version no link is established at all.

But be reminded DAC cables are not officially supported, so you cannot expect any support from MikroTik for such setups. And I would not recommend it for client installations, just for your own sites.
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Tue Sep 21, 2021 5:06 pm

Instead of short DAC cable one can use optical connection as well. Use supported SFP+ module on each side (can be different make as well), they only have to match on optical side (i.e. multi-mode 850nm). And use optical patch cord with appropriate length. Optical SFP+ modules also consume quite low power, so total power consumption won't increase as much as with SFP RJ modules.
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Tue Sep 28, 2021 10:13 pm

The difference is you can get the 0.5m fs.com DAC for 10€ while 2x SFP+ LC module and a fibre to connect them will be 60-100€.

For some unknown reason MikroTik decided not to spend a few bucks to add propper DAC driving circuits to the RB4011 SFP+ port. This makes short distance 10G connections requiring fibre or active DAC. Both much more expensive compared to short 10G passive DAC cables which you can get for 10€ theese days.
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Tue Sep 28, 2021 11:50 pm

The difference is you can get the 0.5m fs.com DAC for 10€ while 2x SFP+ LC module and a fibre to connect them will be 60-100€.

A pair of optical transcievers indeed cost more than 10€, but they are less than 60-100€ (FS lists 850nm SFP+ modules for less than 20€ a piece, 2m patch cord is less than 5€). But if going for pair of transcievers and fibre patch, one has all flexibility possible: freelly select transciever compatible with each of devices (if they come from different vendors, then getting active SFP gadget compatible with both devices sometimes isn't easy) and freely select length of connection (and even make it longer with minimum investment).
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Wed Sep 29, 2021 6:05 pm

That Cisco switch is all Gigabit, so the ports are SFP, not 10G SFP+. I don't know if DAC works at 1Gig.
 
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Re: RB4011iGS+RM with SFP to RJ45 Copper Transceiver Module

Sun Oct 03, 2021 11:36 pm

Yes, I sometimes forget the optical stuff has gotten very cheap to...

But I think we deviated from the OPs question if an RB4011 can be powered by an active PoE 802.3at or 802.3af switch at ether1 altough not explitly specified.
In our experience, it works without problems on 802.3af ports. On 802.3at 15W ports it gets tight in combination with copper SFPs, but we have 2 devices running stable this way

If there are overload issues with the 802.3at switch port and upgrading to 802.3af is not an option, some watts can be saved replacing the RB4011 copper SFP with 850nm/LC or even DAC.

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