Half of every bond lives in the switch, and switches are not all equal. Five minutes with the spec sheet — or the switch's own menu — tells you which DSM modes are even available to you, before a single cable moves.
The bonding failures that fill forums usually share one cause: the NAS was configured for a mode the switch never agreed to. Switches come in three honest classes — dumb, smart and managed — and your class decides your menu. Check it first, and the rest of the setup becomes boring, which is exactly what you want.
☐ The switch is smart or managed — it has a settings page or app
☐ Its spec sheet or menu mentions LACP, 802.3ad or Link Aggregation Groups
☐ A LAG group can be created on the exact two ports the NAS uses
☐ Both ports are the same speed — both gigabit, or both 2.5G
☐ Nothing else already owns those two ports
An unmanaged switch has no settings at all: you plug cables in and it forwards traffic. It cannot do LACP or static aggregation, so two of DSM's bond modes are simply unavailable behind it.
That does not make it useless. Separate interfaces (the LAN/WAN split from the video), Adaptive Load Balancing and Active/Standby all work perfectly through it. Do not buy a managed switch until you can name the feature you are buying it for.
These have a web page or app where the switch itself is configured. Look for a section named LAG, Port Trunking or Link Aggregation — brands label it differently, but the job is identical: create a group, add the two ports the NAS uses, and set the group to LACP.
Save the switch configuration before touching DSM. A group that exists on only one end of the cables is worse than no group at all, which is the subject of the next step.
Order matters, because a half-configured aggregation is an argument between two devices. Work in this sequence:
Doing DSM first leaves the NAS shouting a protocol the switch has never heard of, and the pair spends its life half-negotiated.
The LAN sockets on a home or ISP router are a small unmanaged switch wearing a router's clothes. There is no LAG menu anywhere in its settings, because there is nothing to configure.
Plugging a NAS bond that is set to 802.3ad into router ports creates exactly the mismatch this page exists to prevent. Either use a mode that needs no switch support, or place a small managed switch between the router and the NAS and let it do the aggregation properly.
Search your switch's model number together with LACP or 802.3ad. The datasheet line decides everything. If it says LACP is supported, 802.3ad bonding is available to you.
If it says only "link aggregation" with no mention of LACP, that usually means static aggregation — DSM's Balance XOR territory. And if the sheet says nothing at all, treat the switch as unmanaged, because that is what it is.
Confirm your switch class with this checklist, then watch the video and build the NAS side to match.
▶️ Watch Full VideoNot always. Some switches only do static aggregation, which pairs with DSM's Balance XOR, not with 802.3ad. The switch's menu will show whether LACP can be switched on for a group — that line is the proof.
Only in Adaptive Load Balancing or Active/Standby mode. LACP treats both links as one channel and expects them to end on the same switch, or on a stacked pair acting as one switch.
Yes. Aggregation groups want identical members. A gigabit port and a 100 Mbps port in one group gives confusing, uneven behaviour — fix the slow leg first, because the cause is very often just its cable.