Windows can open several SMB connections through one Ethernet adapter, so multichannel activity doesn't prove both network ports are carrying files. Your second cable can remain unused.
Connecting both F9A Ethernet ports gives Windows two 2.5GbE interfaces to work with. The NAS still needs a compatible multichannel configuration. Start with the active connection, not the advertised bandwidth.
While a large file copies, run Get-SmbMultichannelConnection in an administrator PowerShell window. Find the NAS's name in the output. Entries for other servers tell you nothing about this transfer.
Check the Client Interface Index values rather than counting rows. Two selected rows with the same client index don't establish a file transfer using both Ethernet connections.
Suppose two selected entries show client index 12 paired with two different server indexes. Windows is still reporting one client interface, even though two server interfaces are selected. Both rows can still carry data through a single PC port.
Use Get-NetAdapter -Physical to match those indexes to hardware. SMB's output can include virtual interfaces. Match the names as well, so a virtual adapter doesn't get mistaken for the unused Ethernet port.
Open the full connection details with Get-SmbMultichannelConnection | Select-Object * and find CurrentChannels. It counts connections for that interface pair, not the computer's active cables.
Get-SmbMultichannelConnection -IncludeNotSelected also reveals interface combinations Windows didn't choose. Look for Selected set to False. The ordinary view omits these candidates, hiding a useful distinction between a rejected path and one never discovered.
An unused row doesn't identify a bad cable or broken adapter by itself. Windows may prefer a faster path or another capability, so compare the rejected combination with the selected ones before blaming hardware.
QNAP also specifies equal numbers of participating Ethernet ports on each device. Pairing your two-port PC with one faster NAS port falls outside that documented arrangement, despite the tempting bandwidth arithmetic.
Its matching-speed rule applies within each device, not necessarily across the entire connection. Two 2.5GbE PC ports can pair with two 10GbE NAS ports, with the PC side limiting bandwidth.
Check negotiated link speeds with Get-NetAdapter, not the labels on the case. A nominally 2.5GbE port can be connected at a lower speed. The live connection is what SMB has to work with.
Windows normally combines adapters with matching speeds and capabilities, leaving slower ones idle. A second port operating at 1Gbps won't simply add another gigabit to an otherwise 2.5Gbps connection.
Get-SmbClientNetworkInterface shows the speeds and RSS capabilities SMB sees. Compare both intended ports there. A matching product label isn't enough when the operating system reports different capabilities.
The intended adapter should show Enabled as True for that binding. Look beside its name, not another port's. A disabled SMB binding can leave web browsing working while blocking access to the NAS share through that interface.
A listed adapter can still be excluded by a saved rule. Run Get-SmbMultichannelConstraint and check entries for your NAS. These constraints specify which client interfaces SMB is allowed to use for that server.
An old rule naming only one adapter can explain why a second connection stays unused despite matching speeds. On a managed computer, check why the restriction exists before changing it.
Read the Dialect field in Get-SmbConnection during the copy. Multichannel needs SMB3, not SMB2. A NAS advertising SMB3 can still have a client connected with an older dialect.
If SMB3 is active but no usable second path appears, investigate discovery and reachability separately. The server advertises its network interfaces before Windows tries additional connections, which can then fail through routing or firewall problems.
For a test file larger than 1GB, Robocopy's /J option uses unbuffered I/O rather than File Explorer's buffered copying. Keep the file, destination, and copy direction unchanged when comparing single-port and dual-port results.
Once both physical ports are selected, watch a sustained copy rather than its opening burst. A transfer can slow when write caches fill, even while multichannel remains active. Compare disk throughput with network throughput at the slowdown before treating it as another Ethernet fault.
Connecting both F9A Ethernet ports gives Windows two 2.5GbE interfaces to work with. The NAS still needs a compatible multichannel configuration. Start with the active connection, not the advertised bandwidth.
Connection counts can fool you
Receive Side Scaling, or RSS, distributes network processing across CPU cores. With RSS-capable hardware, SMB can create several connections on one adapter without using another physical port.While a large file copies, run Get-SmbMultichannelConnection in an administrator PowerShell window. Find the NAS's name in the output. Entries for other servers tell you nothing about this transfer.
Check the Client Interface Index values rather than counting rows. Two selected rows with the same client index don't establish a file transfer using both Ethernet connections.
Suppose two selected entries show client index 12 paired with two different server indexes. Windows is still reporting one client interface, even though two server interfaces are selected. Both rows can still carry data through a single PC port.
Use Get-NetAdapter -Physical to match those indexes to hardware. SMB's output can include virtual interfaces. Match the names as well, so a virtual adapter doesn't get mistaken for the unused Ethernet port.
Open the full connection details with Get-SmbMultichannelConnection | Select-Object * and find CurrentChannels. It counts connections for that interface pair, not the computer's active cables.
Get-SmbMultichannelConnection -IncludeNotSelected also reveals interface combinations Windows didn't choose. Look for Selected set to False. The ordinary view omits these candidates, hiding a useful distinction between a rejected path and one never discovered.
An unused row doesn't identify a bad cable or broken adapter by itself. Windows may prefer a faster path or another capability, so compare the rejected combination with the selected ones before blaming hardware.
NAS rules are not universal
QNAP lists RSS and network adapter teaming as unsupported in its SMB Multichannel implementation. Windows Server supports configurations using both. Windows file-server instructions may assume capabilities that your QNAP NAS doesn't offer.QNAP also specifies equal numbers of participating Ethernet ports on each device. Pairing your two-port PC with one faster NAS port falls outside that documented arrangement, despite the tempting bandwidth arithmetic.
Its matching-speed rule applies within each device, not necessarily across the entire connection. Two 2.5GbE PC ports can pair with two 10GbE NAS ports, with the PC side limiting bandwidth.
Check negotiated link speeds with Get-NetAdapter, not the labels on the case. A nominally 2.5GbE port can be connected at a lower speed. The live connection is what SMB has to work with.
Windows normally combines adapters with matching speeds and capabilities, leaving slower ones idle. A second port operating at 1Gbps won't simply add another gigabit to an otherwise 2.5Gbps connection.
Get-SmbClientNetworkInterface shows the speeds and RSS capabilities SMB sees. Compare both intended ports there. A matching product label isn't enough when the operating system reports different capabilities.
A missing interface needs a different fix
When Get-NetAdapter sees a port that Get-SmbClientNetworkInterface omits, inspect that port's SMB client binding. Run Get-NetAdapterBinding -ComponentID ms_msclient before replacing hardware.The intended adapter should show Enabled as True for that binding. Look beside its name, not another port's. A disabled SMB binding can leave web browsing working while blocking access to the NAS share through that interface.
A listed adapter can still be excluded by a saved rule. Run Get-SmbMultichannelConstraint and check entries for your NAS. These constraints specify which client interfaces SMB is allowed to use for that server.
An old rule naming only one adapter can explain why a second connection stays unused despite matching speeds. On a managed computer, check why the restriction exists before changing it.
Read the Dialect field in Get-SmbConnection during the copy. Multichannel needs SMB3, not SMB2. A NAS advertising SMB3 can still have a client connected with an older dialect.
If SMB3 is active but no usable second path appears, investigate discovery and reachability separately. The server advertises its network interfaces before Windows tries additional connections, which can then fail through routing or firewall problems.
For a test file larger than 1GB, Robocopy's /J option uses unbuffered I/O rather than File Explorer's buffered copying. Keep the file, destination, and copy direction unchanged when comparing single-port and dual-port results.
Once both physical ports are selected, watch a sustained copy rather than its opening burst. A transfer can slow when write caches fill, even while multichannel remains active. Compare disk throughput with network throughput at the slowdown before treating it as another Ethernet fault.
