A single Smart Access Gateway (SAG) device creates a single point of failure (SPOF) in your network. When that device fails, your branch loses connectivity until the device is manually replaced or restored. High availability (HA) eliminates this risk by pairing two SAG devices so that traffic automatically fails over to the standby device when the active device fails—without manual intervention.
How HA works
SAG HA requires two SAG devices of the same type configured as an HA pair. The system designates one device as active and the other as standby. If the active device fails, traffic fails over to the standby device automatically. When the active device recovers, traffic switches back.
SAG supports two HA modes:
| Mode | Description | Use when |
|---|---|---|
| Static | Combines two devices into one virtual router. The virtual IP address serves as the default gateway for LAN hosts. | Your network uses static routing |
| Dynamic | Runs health checks on both devices without requiring a virtual IP address. | Your network uses dynamic routing |
Why virtual IP matters for static HA: When a shared virtual IP address is used, both the active and standby devices advertise the same IP to LAN hosts. During failover, LAN hosts do not need to update their default gateway—traffic resumes immediately using the same IP. Without a virtual IP, failover causes a temporary loss of connectivity until LAN hosts detect the new gateway.
Prerequisites
Before you begin, make sure that:
Two SAG devices of the same device type are purchased, and the SAG instance version is 1.8.0 or later
The ports used for HA on both devices are assigned the same role
The IP addresses of the peer ports connecting the two SAG devices fall within the same CIDR block
Configure HA
Log on to the Smart Access Gateway console.
Open the Device Management tab for your SAG instance using one of the following methods:
Click the SAG instance ID, then click the Device Management tab on the instance details page.
In the Actions column, click
> Device Management.
Click Manage HA.
In the HA Information section, click the Edit icon.
In the Configure HA dialog box, select an HA mode and configure the parameters.
Parameter Description HA Mode Select the HA mode: Disable, Static, or Dynamic. Port (Static mode only) Select the device port that uses static routing. Virtual IP (Static mode only) Enter the virtual IP address in dotted decimal notation, for example, 192.168.0.2.NoteFor static HA, the virtual IP address must meet all of the following requirements:
- Falls within the same CIDR block as the port IP address
- Does not overlap with IP addresses already assigned to other ports in the same CIDR block
- Is the same on both the active and standby SAG devices
After configuring the virtual IP address, set the next hop of the Alibaba Cloud-facing route on your core switch to this virtual IP address.
Click Save.