I have a CRS520, which was originally positioned as a switch.
After I upgraded to the 7.17 beta firmware, the RDMA function is working well.
(7.16.2 cannot support : lldp-dcbx. </ip/neighbor/discovery-settings set lldp-dcbx=yes>)

However, due to its excellent CPU performance (up to 2Ghz frequency), I tried to set it as a PPPoE main router.
My upstream broadcasting converter (optical modem) has a 2.5Gbe Ethernet port.
Unfortunately, this 2.5G port cannot negotiate with the 10GBE network port（eth1&eth2） on CRS520 to 2.5G, and can only work at 1G, so I used an 10GBE optical-to-electrical module and plugged it into the sfp28-4 port, using it as the PPPoE upstream WAN port.

I succeeded and turned on fasttrack.now it is running stably.
and I tested its PPPoE performance. At a downloadingspeed of 2.4gbps, the CPU single core occupancy was up to 75%. I think its PPPoE capability should be around 3.0-3.5Gbps.







This performance has met my expectations, because my bandwidth of the line is 2000Mbps. I am satisfied with this product.
now It can be used not only as a switch supporting ROCE, but also as a router supporting PPPoE.


However, its biggest defect is that it has no additional storage space, only 128MB NAND flash. There is no USB interface, nor SATA or M.2 hard disk interface.
I opened the cover and tried to find the solder pads for the USB interface on the PCB, but I didn't find it.

Is there any way to connect USB or other expansion storage from the PCB? I need to run some lightweight docker service on CRS520!
In that way, it becomes a perfect router+switch.

You could look at Mikrotik's rose storage.

Ever since the crs520 was announced with such a powerful CPU I wondered how long it would be until someone tried to use it as a multifunction device.

I suppose you have compelling reasons to start using that CRS520 as a multifunction device beyond simply because you can

but

we must warn about this kind of situations because it can lead to unsatisfactory results if not properly deployed and also be conservative about expectations of performance in that conditions

Ever since the crs520 was announced with such a powerful CPU I wondered how long it would be until someone tried to use it as a multifunction device.

I suppose you have compelling reasons to start using that CRS520 as a multifunction device beyond simply because you can

but

we must warn about this kind of situations because it can lead to unsatisfactory results if not properly deployed and also be conservative about expectations of performance in that conditions

Yes,Due to the high performance CPU, it can be used for routing.not only as a switch.
I have already tried，and the experience is really good.
In the application of PPPoE, its performance is almost close to CCR2216,2116, because PPPoE mainly relies on the performance of a single core CPU.

But its storage space is too small, only 128MB NAND. I really hope it can expand the USB or SATA interface.
If there are corresponding pads on the PCB, I can solder and lead them out myself, thank you!

I am a hardware engineer, I am sure I understand the risks involved. I will bear it myself.
If you have relevant pad information, please share it with me,
Thank you very much for your help,

I'm here with @chechito wondering why TF?

CRS520 comes with list price of almost 2200$ and power consumption exceeding 120W. So one doesn't really save much by not adding a small server to the network, a high-end raspberry pi would dance around CRS520 when it comes to server functions (stock samba vs. ROSE, decent DHCP server vs. whatever ROS provides, full-featured DNS server vs. the cludge of caching server ROS provides) at fraction of price. Yeah, one could run containers on CRS but storage will be a problem anyway (both physical attachment and driver availability).
SoC specs overview only mentions PCIe interface, not SATA or USB. I'd expect for MT to skip those lines when designing board of a switch device ...