MikroTik RB921 Series

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This page is currently under construction. You can edit the article to help completing it.

This page covers the MikroTik RouterBoard921-series, which is a stripped down version of the RouterBoard 922. MikroTik uses this board as base for some other products, like

The board has QCA9557 @ 720MHz; 128MB RAM; 128MB NAND, 64kB config-NOR; 1G Lan-port; QCA9892 5GHz a/n/ac. The concrete antenna differs on the final model.

PCB of a RB921GS-5HPacD-15S

On the right-side of the pcb is still the printing “RB922GS 5HPac”, which shows the origin of the design. A bit above is the not populated MiniPCI-e socket, on the lower right end is the unpopulated USB-connector.

ModelVersionSoCCPU MHzFlash MBRAM MBWLAN HardwareWLAN2.4WLAN5.0100M portsGbit portsModemUSB
RB921GS-5HPacD-15S (mANTBox 15s)Qualcomm Atheros QCA9558720128NAND128Qualcomm Atheros QCA9882-a/n/ac-1--

FIXME Find out flash layout, then add the flash layout table here (copy, paste, modify the example).

Please check out the article Flash layout. It contains examples and explanations that describe how to document the flash layout.

For full documentation have a look at Common Procedures for Mikrotik RouterBoard Products

How you install OpenWrt, using Mikrotik mANTBox 15s as example:

  1. You need a DHCP server because the device is using DHCP to get the first IP. You can use dnsmasq (see below) for this task. Start DHCP server and do the following:
    1. boot Mikrotik Routerboard. Search the IP of the device in DHCP server log. Log into web interface with user: “admin” and empty password
    2. System → Routerboard → Settings → Boot device: Try ethernet once then NAND. This configuration is only valid for the next reboot. This means that you need to activate this again if you your first try to install OpenWRT was not successful.
    3. System → Routerboard → Settings → Boot protocol: DHCP
    4. System → Routerboard → Settings → Force Backup Booter: Checked (if supported by your routerboard - !IMPORTANT)
    5. System → shutdown (NO reboot)
  2. Start DHCP server and TFTP server (if not already done):
    1. configure fix IP for TFTP server, e.g.
    2. download ramfs images. Copy images to e.g. /srv/tftp
    3. start dnsmasq with the following command (replace enp0s25 with your network adapter)
       dnsmasq -i enp0s25 --dhcp-range=, --dhcp-boot=openwrt-19.07.4-ar71xx-mikrotik-vmlinux-initramfs.elf --enable-tftp --tftp-root=/srv/tftp/ -d -u age -p0 -K --log-dhcp --bootp-dynamic
    4. start mANTBox
      1. if you see in dnsmasq log that vmlinux-initramfs.elf image was send to 192.168.1…. then mANTBox is booting OpenWRT
      2. wait for one/two minutes…
      3. on the Mikrotik device a non-persistent firmware is installed. You can now access the web interface of OpenWRT. Note: If you do reboot the device now the original Mikrotik firmware is booted!
    5. Connect to newly flashed OpenWRT (via web interface or ssh)
    6. Device should reboot automatically.
    7. Done.


FIXME These are generic instructions. Update with your router's specifics.

  • Browse to LuCI Upgrade URL
  • Upload image file for sysupgrade to LuCI
  • Wait for reboot

If you don't have a GUI (LuCI) available, you can alternatively upgrade via the command line. There are two command line methods for upgrading:

  • sysupgrade
  • mtd

Note: It is important that you put the firmware image into the ramdisk (/tmp) before you start flashing.


  • Login as root via SSH on, then enter the following commands:
cd /tmp
wget http://downloads.openwrt.org/snapshots/trunk/XXX/xxx.abc
sysupgrade /tmp/xxx.abc


If sysupgrade does not support this router, use mtd.

  • Login as root via SSH on, then enter the following commands:
cd /tmp
wget http://downloads.openwrt.org/snapshots/trunk/XXX/xxx.abc
mtd write /tmp/xxx.abc linux && reboot

Basic configuration After flashing, proceed with this.
Set up your Internet connection, configure wireless, configure USB port, etc.

FIXME Please fill in real values for this device, then remove the EXAMPLEs

The default network configuration is:

Interface Name Description Default configuration
vlan0 (eth0.0) EXAMPLE LAN ports (1 to 4) EXAMPLE None
vlan1 (eth0.1) EXAMPLE WAN port EXAMPLE DHCP

hardware.button on howto use and configure the hardware button(s). Here, we merely name the buttons, so we can use them in the above Howto.

FIXME Please fill in real values for this device, then remove the EXAMPLEs

The MikroTik RB921 has the following buttons:

EXAMPLE Reset reset
EXAMPLE Secure Easy Setup ses
EXAMPLE No buttons at all. -

RB921GS-5HPacD-15S / mANTBox 15s

This seems in fact a RB921 board combined with the MikroTik mANT 15s sector-antenna.


the 2 sectors-antennas with frontcover removed the stacked antenna-array

back with pcb and RF-splitter for sectors

Backside label:
Insert photo of backside label

Note: This will void your warranty!

Unscrew the 8 screws visible on the back with a T9 screwdriver.

RB921GS-5HPacD-19S / mANTBox 19s

Main PCB:
Insert photo of PCB

port.serial general information about the serial port, serial port cable, etc.

How to connect to the Serial Port of this specific device:
Insert photo of PCB with markings for serial port

FIXME Replace EXAMPLE by real values.

Serial connection parameters
for MikroTik RB921
EXAMPLE 115200, 8N1

port.jtag general information about the JTAG port, JTAG cable, etc.

How to connect to the JTAG Port of this specific device:
Insert photo of PCB with markings for JTAG port



Space for additional notes, links to forum threads or other resources.

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  • Last modified: 2021/08/31 15:51
  • by tmomas