On a Windows Server 2012-based computer or a Windows 8-based computer that connects to a server message block (SMB) 3.0 file share, SMB Multichannel ignores non-routable IP addresses if the network interface has both routable and non-routable IP addresses configured. This behavior occurs even though SMB Multichannel typically tries to connect with additional interfaces if multiple network interfaces exist, and tries to establish multiple TCP/IP connections for a Receive-Side Scaling (RSS) capable network interface.
Note Non-routable IP addresses include IPv6 link-local addresses and Automatic Private IP Addressing (APIPA) IPv4 addresses.
Consider the following example scenario:
The SMB client has the following configuration:
Multiple network interfaces are available and enabled for both IPv4 and IPv6.
A static routable IPv4 address is configured for each network interface.
The only IPv6 address assigned to each network interface is a link-local address.
The network interfaces are RSS capable.
The SMB server has the following configuration:
A single network interface is available and is enabled for IPv6 only.
The only IPv6 address that is assigned to the network interface is a link-local address.
The network interface is RSS-capable.
In this scenario, only one SMB session is established, and the SMB client creates a single TCP/IP connection by using the IPv6 link-local address on only one of the network interfaces. Other network interfaces are not used. Additionally, multiple TCP/IP connections are not created, even though the network interface is RSS-capable.
This behavior is by design. SMB Multichannel uses non-routable IP addresses for a network interface only if no routable IP addresses are available for the interface. If a network interface has both non-routable and routable IP addresses configured, SMB Multichannel ignores the non-routable IP addresses.
In the example scenario, only one network interface (interface A) is used for the SMB session because the link-local addresses of the other interfaces are ignored by SMB Multichannel, and the client can connect only to the link-local address of the server. Additionally, only one TCP/IP connection is created for interface A because the link-local address of A is ignored by SMB Multichannel, and the client can connect only to the link-local address of the server.
To work around this behavior, use one of the following methods to enable multiple connections for a network interface:
Configure routable IP addresses for network interfaces that must take advantage of SMB 3.0 Multichannel.
Configure only non-routable IP addresses (APIPA or link-local addresses) for network interfaces that must take advantage of SMB 3.0 Multichannel.
The first method is the recommended workaround.
In the second method, both the SMB client and SMB server must be on the same network segment because the IP addresses are non-routable.
For more information about SMB Multichannel, go to the following Microsoft Server and Management Blog article:
APIPA IPv4 addresses use the 169.254.0.0/16 prefix. IPv6 link-local addresses use the FE80:: /64 prefix. For more information about APIPA IPv4 and IPv6 link-local addresses, go to the following Windows Server website: