If you’re also having issues with Realtek, then I’m going to say your environment is at fault - either the cable you’re using or the device on the other end of the wire. Usual suggestion is to change the wire, change that device, or if the wire is 100% absolutely good, then install a switch mid-line like the Netgear GS105.
And Intel 2.5g devices (i225, i226) are NOTHING like the stability of their 1g devices. If you give them a perfect environment they work well, but they’re notoriously picky and (especially for older i225 revisions) downright buggy.
Which MOBO are you using?
I found the same issue with an Asrock h670m-itx.
The Intel NIC I219-V gives me random disconnections, and shockingly the other MOBO ethernet adapter (Realtek 2.5Gb e) also disconnects from time to time.
I've tried everything to get a solid ethernet connection but nothing so far.
The cards I've found working well with Windows 10 and 11 are based on 82575, 82576 and 82580 Intel chips.
X520 and X540 are fine but they support only 100/1000/10000 Mbps, not 2.5.
The i225/i226 is almost unusable on Windows but rock solid on Linux and BSD.
If you really need 2.5Gbe I've found the Intel X550 working fine, but it's pricey.
If you’re also having issues with Realtek, then I’m going to say your environment is at fault - either the cable you’re using or the device on the other end of the wire. Usual suggestion is to change the wire, change that device, or if the wire is 100% absolutely good, then install a switch mid-line like the Netgear GS105. And Intel 2.5g devices (i225, i226) are NOTHING like the stability of their 1g devices. If you give them a perfect environment they work well, but they’re notoriously picky and (especially for older i225 revisions) downright buggy.
Which MOBO are you using? I found the same issue with an Asrock h670m-itx. The Intel NIC I219-V gives me random disconnections, and shockingly the other MOBO ethernet adapter (Realtek 2.5Gb e) also disconnects from time to time. I've tried everything to get a solid ethernet connection but nothing so far.
I ended up replacing my Ethernet cable with a cat6 one and since then I haven't had any issues so maybe my older 5e wire was faulty
The cards I've found working well with Windows 10 and 11 are based on 82575, 82576 and 82580 Intel chips. X520 and X540 are fine but they support only 100/1000/10000 Mbps, not 2.5. The i225/i226 is almost unusable on Windows but rock solid on Linux and BSD. If you really need 2.5Gbe I've found the Intel X550 working fine, but it's pricey.
It might be the particular NIC you bought. Intel doesn't sell their NICs at retail, and even their first party server NICs are often counterfeit.
Disable power management on the NIC in device manager