I'm running Windows Server 2012 R2 and want to connect a Synology Rackstation via iSCSI to my server. The connection is done via four seperate LAN ports. The iSCSI part works fine, but if I copy stuff from the server to the NAS only one ethernet port (always the same) is active instead of four. Load balancing for MPIO is set to Round Robin.

The four ports have different subnets e.g. (Ping works)



Subnet mask:

MPIO is enabled for every LUN and I verified this via mpclaim -s -d

I cannot find different paths, though.

What is the problem? Do you need more information to help me? If so, please ask.

Edit: Still looking for a solution :-(

  • What is the subnet mask for those interfaces? – longneck May 12 '17 at 14:04
  • Subnet mask is – Boernii May 12 '17 at 14:12

With a subnet mask of, all of your interfaces are on the same subnet. Use instead.

  • 1
    and while you're at it: maybe change 172.168.x.y to 172.16.x.y. The former is from a publicly assigned IP space, the latter is for private use. – Andreas Rogge May 12 '17 at 14:37
  • Thanks. There is still just 1 Ethernet port used though. What am I overseeing? – Boernii May 12 '17 at 15:02

In order to implement iSCSI connection using MPIO, you should check:

  • Netmask. It should be for your particular case.
  • the Microsoft iSCSI Initiator, whether all 4 Synology IPs are added to Discovery
  • the iSCSI support enabled in MPIO feature.

It might be useful to review the tutorial from Synology web-site: https://www.synology.com/en-global/knowledgebase/DSM/tutorial/Virtualization/How_to_Use_iSCSI_Targets_on_Windows_Computers_with_Multipath_I_O

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