802.3ad LACP always uses same interface when reading from server

[Ridago]

I am trying to setup LACP between my Debian server and TP-Link T1600G-18TS switch. I have set up mode-4 bonding on two of the interfaces on the server and setup LACP on the switch. When trying to transfer files to multiple clients (tested with SMB and Rsync) only one interface is used and it is always the same one, while the other interface is not used at all. If I unplugg the active interface, the traffic switches over to the unused interface just fine. Plugging the interface back in moves all the traffic back to that interface. Writing to the server from multiple clients splits the traffic over the two interfaces just fine as long as I use the SRC MAC or SRC + DST MAC hashing algorithm on the switch.

 

I have experimented with the hashing algorithm on the switch, trying DST MAC, SRC MAC, and DST+SRC MAC, with no effect on the result. I have not yet tried changing the hashing algorithm on the server, which is still at default layer 2. From what I have read I can't see how any of the options server side would change the behaviour I am experiencing.

[brwainer]

traffic leaving the server entering the switch, is determined by the hashing algorithm on the server. The hashing algorithm on the switch only affects the traffic going outbound to the server, not inbound from it.

[Ridago]

Fixed it by setting the hashing algorithm on the server to Layer2+3 instead of the default Layer2 and leaving the switch at default SRC+DST MAC