I have just arrived at the same question when I found that all traffic was going via one member in one of my tests. I have a Synology 1511+ using LAG (LACP) to SLM2008 with two PCs (non LAG) transmitting. I tried changing one of the IP address but made no difference, which makes me think that it's not IP (DST and/or SRC IP hash). I have a strong suspicion that it could be MAC hashing as when I tested with a different set of computers, I was able to utilise both members. If I do manage to get another NIC (that hopefully will hash the other way) and test, I will post back. WRT your NAS' hash policy, it depends on how many devices will be doing most of the transfers to/from the NAS, and what kinds of applications. If you have a large number (eg more than 4), I would definitely include L4 info as the diversity in the L4 ports should give you a good distribution. But this is only when your NAS is transmitting. On the other hand, if you're like me where I have two main devices that will do 90% of the transfers and all via SMB, I would choose L3 and make one of the IP +1 of the other.
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