How to Set Up Link Aggregation on Synology NAS
Synology DSM supports multiple Link Aggregation modes, including Adaptive Load Balancing, IEEE 802.3ad Dynamic Link Aggregation, Balance XOR, and Active/Standby. The right configuration depends on your switch, workload, clients, and whether your priority is aggregate throughput or redundancy.
Understanding these differences before configuring LACP can prevent one of the most common disappointments with multi-port NAS networking.
What Is Link Aggregation on a Synology NAS?
Link Aggregation combines multiple physical Ethernet interfaces into a logical interface called a bond. Suppose a NAS contains two 1GbE ports. Instead of treating LAN 1 and LAN 2 independently, DSM can combine them into Bond 1.
With an appropriate configuration, this can provide two major benefits:
- Greater aggregate bandwidth across multiple network connections
- Failover if one physical connection stops working
Synology specifically describes bonding as a way to increase available bandwidth while providing resilience when a physical link fails. The important word, however, is aggregate.
LACP Does Not Automatically Double One Client’s Speed
This is the most important concept to understand before purchasing cables or a managed switch.
Imagine this configuration:
NAS → 2 × 1GbE → LACP-capable switch
The NAS now has up to 2Gbps of aggregate network capacity. But that does not necessarily mean a single Windows workstation copying one file can reach 2Gbps. LACP distributes network flows according to hashing behaviour implemented by the systems and switch. An individual network flow normally remains associated with one physical link. Where LACP becomes valuable is when multiple connections are active.
For example:
Client A → 1Gbps
Client B → 1Gbps
The NAS may now serve approximately 2Gbps of aggregate traffic instead of forcing both clients to share one 1GbE interface, assuming storage and the rest of the network can keep up.
When LACP Makes the Most Sense
Link Aggregation is especially useful when a Synology NAS serves many systems simultaneously.
Common workloads include:
- Office file sharing
- Multiple backup jobs
- Virtualization storage
- Surveillance
- Media libraries
- Workstation backups
- Large creative teams
- Multiple servers accessing shared storage
A NAS serving 20 employees can benefit substantially from additional aggregate bandwidth even when each employee’s individual connection remains limited by a single link.
That makes LACP more of a multi-client capacity technology than a straightforward single-workstation speed upgrade.
Check the Switch Before Configuring LACP
IEEE 802.3ad Dynamic Link Aggregation requires compatible networking equipment.
Your switch needs to support LACP (Link Aggregation Control Protocol), and the relevant switch ports must be placed into the same aggregation group. This is one of the biggest differences between LACP and Synology’s Adaptive Load Balancing option. Do not configure LACP on DSM first and assume an unmanaged switch will understand the bond.
Before beginning, verify:
- Your Synology model has multiple compatible network interfaces.
- The switch supports IEEE 802.3ad/LACP.
- You have administrative access to the switch.
- All required cables and ports operate at their expected speeds.
- The network design does not already use those interfaces for another incompatible configuration.
Step 1: Test Each Synology Network Port
Before creating a bond, verify that each individual Ethernet connection works correctly.
A bad cable, damaged switch port, or interface negotiating at the wrong speed can create confusing problems once the interfaces are combined. Check DSM and the managed switch to confirm that every link negotiates at its intended speed.
For example, a two-port 2.5GbE Synology should show both connections at 2.5Gbps before you attempt to create a 5Gbps aggregate link.
Fix physical networking problems first.
Step 2: Configure the Switch’s LACP Group
The exact process varies among switch manufacturers, but the general objective is the same.
Select the switch ports connected to the Synology and create an LACP/802.3ad Link Aggregation Group (LAG).
For example:
Switch Port 5 → Synology LAN 1
Switch Port 6 → Synology LAN 2
Ports 5 + 6 → LACP Group
If VLANs are involved, make sure the aggregated interface receives the appropriate VLAN configuration.
Multi-switch configurations require additional caution. Synology guidance for dynamic aggregation notes that when multiple switches are involved, they need an architecture that properly supports the aggregated connection, such as appropriate stacking/configuration.
Step 3: Create the Bond in DSM
Next, open DSM and navigate to:
Control Panel → Network → Network Interface
Choose:
Create → Create Bond
Select the physical interfaces you want to combine. DSM supports several Link Aggregation modes, including IEEE 802.3ad Dynamic Link Aggregation. For an LACP-capable managed switch, select the dynamic 802.3ad option.
Complete the configuration and assign the bond’s network settings. Once created, DSM treats the bond as a logical network interface rather than requiring services to work separately with each physical LAN connection.
Step 4: Configure the Bond’s IP Address
The new bond needs appropriate network configuration.
Depending on the environment, that may include:
- Static IP address
- Subnet mask
- Gateway
- DNS configuration
- VLAN
- MTU
For servers and NAS devices, static addressing is often preferable because clients, backup applications, monitoring systems, and other infrastructure may depend on a predictable address.
If changing from separate interfaces to a bond, confirm that applications and mapped resources still reference the correct NAS address.
Step 5: Test Failover
Higher throughput is only one benefit of Link Aggregation. The other is redundancy. After verifying that normal network access works, carefully test link failure during a suitable maintenance window. Disconnect one physical Ethernet connection and confirm that the NAS remains reachable through the remaining member of the bond. Reconnect it and verify that the link returns to the aggregation group. A bond that looks correct in DSM but fails when one cable is removed has not achieved the redundancy you expected.
Step 6: Test Multiple Clients
Do not test LACP using only one file transfer from one workstation and immediately conclude that it is not working. Test multiple simultaneous connections.
For example, transfer large files between the NAS and several wired workstations at the same time.
Monitor:
- Individual client throughput
- Aggregate NAS network utilization
- Disk utilization
- CPU utilization
- Switch LAG statistics
The goal is to determine whether traffic is being distributed across the physical interfaces.
LACP vs Adaptive Load Balancing
Not every environment needs LACP.
Synology also supports Adaptive Load Balancing (ALB), which was specifically designed to provide load balancing and failover without requiring specialized Link Aggregation support from the switch. That makes ALB attractive when you have multiple NAS interfaces but an unmanaged or otherwise incompatible switch.
The choice can be simplified as:
Managed switch with properly configured LACP → Consider IEEE 802.3ad
No LACP-capable switch → Consider Adaptive Load Balancing
Redundancy only → Active/Standby may be sufficient
Do not select the most complicated mode simply because it sounds faster.
LACP vs SMB3 Multichannel
This distinction is particularly important for Synology users looking for faster SMB transfers.
Link Aggregation and SMB3 Multichannel solve different problems.
LACP primarily increases aggregate capacity across network connections.
SMB3 Multichannel allows compatible SMB clients to establish multiple network connections and potentially use multiple interfaces for one SMB session.
Synology currently supports SMB3 Multichannel on compatible x86 systems running DSM 7.1.1 or later with SMB Service 4.15 or later. Compatible clients include Windows 8/Server 2012 or newer and macOS 11.3 or newer.
There is one critical limitation:
DSM does not allow SMB3 Multichannel and Link Aggregation to be enabled concurrently.
Therefore, choose according to the workload rather than enabling both.
Which Is Better for a Single Fast Workstation?
If the objective is making one SMB workstation exceed the speed of one Ethernet interface, LACP may not be the best solution.
SMB3 Multichannel can be more appropriate when both the NAS and client have compatible networking.
Alternatively, upgrading to a faster single interface can provide a simpler architecture.
For example:
2 × 1GbE LACP can be excellent for multiple users.
1 × 10GbE can provide much greater bandwidth to a single suitably equipped workstation.
Synology itself offers dual-port 10GbE hardware that supports Link Aggregation for increased simultaneous throughput, load balancing, and port failover.
Don’t Expect Networking to Fix Slow Storage
Increasing network capacity does nothing if the storage subsystem is already the bottleneck.
A Synology NAS may be limited by:
- Number of disks
- HDD performance
- RAID configuration
- SSD performance
- CPU utilization
- Encryption
- Concurrent backup operations
- RAID rebuilds
- Other applications
Monitor DSM while running throughput tests.
If disks are already saturated while network interfaces remain underutilized, additional Ethernet bandwidth will not solve the problem.
Be Careful With Jumbo Frames
Link Aggregation and jumbo frames are separate technologies.
You do not need MTU 9000 simply because you configured LACP. Jumbo frames should only be enabled when the entire relevant network path supports the selected MTU consistently. That includes the NAS, switches, and clients. An MTU mismatch can create connectivity or performance problems that are much harder to diagnose than the small performance improvement jumbo frames may provide. Start with the standard MTU and optimize later if testing demonstrates a genuine benefit.
Common Synology LACP Problems
If the bond is not performing as expected, check the basics before changing advanced DSM settings.
Typical problems include:
- LACP not enabled on the switch
- Wrong switch ports assigned to the LAG
- Faulty Ethernet cable
- One port negotiating at a lower speed
- Incorrect VLAN configuration
- MTU mismatch
- Incompatible multi-switch configuration
- Storage unable to supply enough throughput
- Testing with only one network flow
- Expecting two ports to behave like one faster physical port
Also verify that SMB3 Multichannel has not been configured alongside Link Aggregation, since DSM explicitly treats the two configurations as mutually exclusive.
Should You Use LACP or Upgrade to 10GbE?
For a NAS serving many users, Link Aggregation can be an economical way to increase total available bandwidth while adding network redundancy.
For a video editor, virtualization server, or workstation that individually needs several gigabits per second, faster Ethernet may be the better investment.
A useful planning rule is:
Many simultaneous clients → LACP can be valuable.
One extremely fast client → Consider 5/10GbE or SMB3 Multichannel.
Need both throughput and interface redundancy → Faster multi-port networking plus appropriate aggregation may be justified.
Synology’s enterprise guidance similarly recommends considering faster network interfaces and Link Aggregation as part of storage-network optimization rather than treating bonding as the only path to higher performance.
About Epis Technology
Epis Technology helps businesses design Synology networking around real workloads instead of theoretical link speeds. Services include Synology deployment and performance optimization, LACP and Link Aggregation configuration, managed-switch setup, VLAN architecture, 2.5GbE, 10GbE and 25GbE networking, SMB optimization, large storage solutions, virtualization, business backups, cybersecurity, and disaster recovery. Epis Technology can evaluate whether Link Aggregation, SMB3 Multichannel, faster Ethernet, or a combination of storage and network upgrades provides the most practical path to higher NAS performance.