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We have several servers on our rack. All of them running Windows 2016 or Windows 2019. We always do nic teaming. For example, by combining 4 NICs we get speeds at 4Gbit (400mb/sec or so) between servers via SMB.

However, we have one Dell R420 server, running Windows 2016, which has 6 x Broadcom NetXtreme Gigabit Ethernet NIC adapters.

We have tried several configurations for that server, combining via Windows NIC teaming all 6 NICS, or 2 of them. We cannot ever get higher than 1gbit transfers out of that server.

We cannot figure out why this happens. The Link of Microsoft Network Adapter Multiplexor interface does show 6Gbit:

PS C:\Users\Administrator> Get-SmbServerNetworkInterface

Scope Name Interface Index RSS Capable RDMA Capable Speed IpAddress

 10              True        False        6 Gbps 10.1.1.100
 10              True        False        6 Gbps fe80::801a:3dc4:912f:b5c5

But speeds from/to that server are always at 1Gbit. Also multichannel looks it's working:

SMB server: >> Get-SmbServerNetworkInterface EnableMultichannel ------------------ True

It happens only for this server. All servers are connected to the same switch.

bjoster
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Alex K.
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  • What's the *teaming mode* & *load balancing mode* you have been using? ([NIC Teaming settings](https://docs.microsoft.com/en-us/windows-server/networking/technologies/nic-teaming/nic-teaming-settings)) – Esa Jokinen Nov 14 '20 at 15:42
  • Hi there. It's the same as with all other servers: Teaming mode: Switch Independent. Load Balancing mode: Dynamic – Alex K. Nov 14 '20 at 16:09
  • How are you measuring the 1Gb xfer rate? How big are the messages? – Rick James Dec 04 '20 at 19:57

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