MikroTik Routerboard RB493G

The RB493G has 9 Gigabit Ethernet ports and 3 mini-PCI slots: add a mini-PCI card for 802.11 a/b/g/n 2.4GHz/5GHz WiFi.
You have to pretty much build-your-own (buy the board, snap in the WiFi, screw it all into a sturdy metal case), but it's worth this small effort to end up with such a highly capable OpenWrt-compatible 2.4/5GHz WiFi router.
There are vendors that will sell you an RB493G fully assembled with WiFi, then all you need to do is install OpenWrt to have a powerhouse router.

VLANs on the RB493G
There is a lot of confusion/mis-information about this router's VLAN support. It DOES support 802.1Q Trunking with OpenWrt version 18 in spite of outdated Internet assertions that it does not.
This device uses two Atheros AR8316 switch chips. AR8316 VLAN capabilities:

  • Supports 802.1Q 'Trunk' switching which allows you to put one untagged VLAN (the 'native' VLAN1) and any number of tagged VLANs on the same port.
  • Does NOT support 'hybrid' or 'general' VLAN switching which allows you to map any VLAN, tagged or untagged, to/from any port.

In order to set up a segregated guest network using VLANs, an 802.1Q Trunk is sufficient: the lack of 'hybrid' VLAN switching on the RB493G is of minimal consequence, unless you are attempting to use it as a managed switch rather than a router/firewall.

See the Mikrotik documentation: https://wiki.mikrotik.com/wiki/Manual:Switch_Chip_Features for an explanation of trunk, access and hybrid port capabilities for the switch chips.
The biggest fault of the Mikrotik switch documentation is that it does not clearly state that an 802.1Q Trunk DOES allow tagged and untagged traffic on the same port when the RB493G is used as a router.

See Common Procedures for Mikrotik Router Boards for a general discussion of the procedures to install OpenWrt on Mikrotik RouterBoards.
The Common Procedures apply directly to the RB493G and are generally kept more up-to-date than these product-specific wiki pages, so it is a good idea to initially refer to the Common Procedures.
For example, the Common Procedures have been fully updated to reflect the considerably simplified Version 18 procedures to install OpenWrt, whereas many of these product-specific wiki's have yet to be updated.

Before you start installing OpenWrt, save your RouterOS License .key file. This will allow you to use Mikrotik's NetInstall to re-install RouterOS if something goes wrong installing OpenWrt.
Save your license by using Mikrotik WinBox: it's under System→License→Export Key. The Mikrotik WebFig web interface does not export license files, you must use WinBox.

Please check out the article flash.layout. It contains an example and a couple of explanations.

root@OpenWrt:/# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 0000b000 00001000 "routerboot"
mtd1: 00001000 00001000 "hard_config"
mtd2: 00002000 00001000 "bios"
mtd3: 00001000 00001000 "soft_config"
mtd4: 00040000 00020000 "booter"
mtd5: 003c0000 00020000 "kernel"
mtd6: 07c00000 00020000 "ubi"

The two partitions used to install OpenWrt are kernel and ubi. Their sizes are in bytes with hex, which translates to 3840KiB for kernel and 126976KiB for ubi.

The Mikrotik RouterBoot bootloader will use DHCP/BOOTP/TFTP to load an LZMA compressed image in ELF format and execute it.

Select one of the following approaches to set up a DHCP/BOOTP/TFTP Server:

Use Tiny PXE as the netboot server

The freeware Tiny PXE project is a standalone portable Windows application that implements a DHCP server, BOOTP server, and TFTP server. This is possibly the easiest way to netboot a RB493G since Tiny PXE implements rfc951 BOOTP.

With rfc951 BOOTP, there is no need to enter the RouterBoot console and change the boot protocol from BOOTP to DHCP. Tiny PXE will directly respond to the BOOTP request of the RouterBoard.

To enable rfc951 BOOTP in Tiny PXE, the option 'rfc951=1' must be set in the [dhcp] section of config.ini file of Tiny PXE.

Download the initramfs-lzma.elf file to your PC, enter it as the Boot file name in Tiny PXE, select your 192.168.88.X connection as the Option 54 DHCP server (be sure your PC is set to a static IP in the range), and put Tiny PXE online.

If you power up the RouterBoard and continue holding the reset button, it will automatically search for a BOOTP server: no need to change any of the RouterBoot settings from their default settings with this approach.

When using BOOTP as the boot protocol, be sure to disconnect from any other network devices (routers) since BOOTP has no provisions for Proxy DHCP or authoritative DHCP across multiple simultaneous BOOTP servers: there must be only one DHCP/BOOTP/TFTP server running on the network.

Use another (existing) OpenWrt router as the netboot server

This is an easy way to achieve a live boot of your RB493G, but it requires that you already have an OpenWrt router with net-access available. You will need to obtain an elf image for the RB493G and make it available to the other router. If you have enough memory available on the other router, you can put the image on the /tmp folder there, e.g., like this:

ssh root@
wget --directory-prefix=/srv/tftp http://downloads.openwrt.org/releases/18.06.1/targets/ar71xx/mikrotik/openwrt-18.06.1-ar71xx-mikrotik-vmlinux-initramfs-lzma.elf

Now enable dnsmasq's built in tftp server, and point it to the correct locations, e.g., like this: Setting up netboot in Luci, note the full path for the filename. That's it, Save and apply, connect the Eth1/WAN port of RB493G (the Ethernet port near the serial connector) to one of the other routers LAN ports, and continue to Setup the Routerboard.

Make sure you assigned a static lease for the MAC address of the Routerboards eth1 port, otherwise bootp wont work.

Use a Debian computer as the netboot server

You need a DHCP/BOOTP and TFTP server on your host machine. We use dnsmasq here since it can provide both services. Install dnsmasq with:

sudo apt-get install dnsmasq

Changes in /etc/dnsmasq.d/rb493g.conf:

  1. make sure the LAN has internet access:
    ping openwrt.org
  2. only listen on the interface which is directly connected to the same LAN like the WAN-port (Eth1/PoE) of the RouterBoard via a layer2 switch, e.g.
  3. set default gateway, e.g.
  4. allow a DHCP range which is within netmask of your LAN but does not conflict with other DHCP-service, e.g.
  5. allocate an IP address to the board, e.g. (replace the XX with the MAC address of your board!)
  6. make dnsmasq authoritative to overrule the DHCP server of your router
  7. enable dnsmasq's built-in TFTP-server
  8. set the root directory-for files available via TFTP.
  9. set filename of kernel image for tftp-server/BOOTP:

Download 18.06.1 initramfs-lzma.elf kernel image into the root-directory of the TFTP-server:

sudo wget --directory-prefix=/srv/tftp http://downloads.openwrt.org/releases/18.06.1/targets/ar71xx/mikrotik/openwrt-18.06.1-ar71xx-mikrotik-vmlinux-initramfs-lzma.elf

Finally restart dnsmasq:

sudo /etc/init.d/dnsmasq restart

Option 1 - Use the serial console terminal to force a netboot

  1. Connect to the serial COM port of the RB493G with a null modem adapter (Baud 115200, 8 bits, no parity, 1 stop bit, no flow control)
  2. Open a console terminal window on the COM port using software such as PuTTY (or a Linux terminal window)
  3. Press a key in the console terminal window within two seconds after powering up the board (you will see a prompt)
  4. Press o to change the boot device
  5. Press 1 to boot from ethernet once
  6. Press p to change the boot protocol. Skip this step and next step if using an rfc951 DHCP/BOOTP/TFTP netboot server such as Tiny PXE (with rfc951=1 in the [dhcp] section of config.ini file)
  7. Press 2 to boot using DHCP (instead of the default BOOTP)
  8. Press x to leave setup

Option 2 - Use the Reset button to force a netboot

You can force the RouterBoard to attempt a netboot by simply pressing and holding the Reset button when powering up:

  1. Power down the RouterBoard
  2. Press and hold the Reset button
  3. Power up the RouterBoard
  4. Once the RouterBoard beeps, there is no need to continue holding the Reset button (the beep indicates it is now performing a netboot or loading from flash)

If the attempted ethernet netboot fails, it will then boot from flash (just like the 'boot from ethernet once' option chosen above in Option 1). Note this method will use the boot protocol already set in Option 1 above. The default boot protocol is BOOTP, not DHCP, so the RouterBoard will attempt a BOOTP netboot if the Reset button is held without performing the boot protocol change described in Option 1 ('p', then '2'). If your DHCP/BOOTP/TFTP netboot server is rfc951 BOOTP-capable, using the Reset button is a very easy way to force the RouterBoard to netboot right out of the package.

If everything is setup correctly it should look like:


RouterBOOT booter 2.29

RouterBoard 493G

CPU frequency: 680 MHz
  Memory size: 256 MB

Press any key within 2 seconds to enter setup..
writing settings to flash... OK
trying bootp protocol... OK
Got IP address:
resolved mac address 00:14:0B:3F:BB:C3
transfer started ............................... transfer ok, time=1.46s
setting up elf image... OK
jumping to kernel code
[    0.000000] Linux version 3.3.8 (renne@renne) (gcc version 4.6.3 20120201 (prerelease) (Linaro GCC 4.6-2012.02) ) #1 Mon Sep 17 12:57:18 CEST 2012
[    0.000000] bootconsole [early0] enabled
[    0.000000] CPU revision is: 00019374 (MIPS 24Kc)
[    0.000000] SoC: Atheros AR7161 rev 2
[    0.000000] Clocks: CPU:680.000MHz, DDR:340.000MHz, AHB:170.000MHz, Ref:40.000MHz
[    0.000000] Determined physical RAM map:
[    0.000000]  memory: 08000000 @ 00000000 (usable)
[    0.000000] User-defined physical RAM map:
[    0.000000]  memory: 10000000 @ 00000000 (usable)
[    0.000000] Initrd not found or empty - disabling initrd
[    0.000000] Zone PFN ranges:
[    0.000000]   Normal   0x00000000 -> 0x00010000
[    0.000000] Movable zone start PFN for each node
[    0.000000] Early memory PFN ranges
[    0.000000]     0: 0x00000000 -> 0x00010000


Please press Enter to activate this console. [   21.710000] device eth0 entered promiscuous mode
[   21.720000] device eth1.1 entered promiscuous mode
[   21.720000] device eth1 entered promiscuous mode
[   23.110000] eth0: link up (1000Mbps/Full duplex)
[   23.130000] br-lan: port 1(eth0) entered forwarding state
[   23.130000] br-lan: port 1(eth0) entered forwarding state
[   23.600000] eth1: link up (1000Mbps/Full duplex)
[   23.610000] br-lan: port 2(eth1.1) entered forwarding state
[   23.620000] br-lan: port 2(eth1.1) entered forwarding state
[   25.130000] br-lan: port 1(eth0) entered forwarding state
[   25.620000] br-lan: port 2(eth1.1) entered forwarding state

Press Enter and you are in the console of OpenWRT running from RAM and booted via DHCP/BOOTP/TFTP.

Note that you may need to set dns servers to get net-access while running the netbooted image. Enter a working dns for you in

vi /tmp/resolv.conf.auto

then restart dnsmasq to make the change effective (cross-check that you indeed have net-access afterwords):

/etc/init.d/dnsmasq restart

You need a working Netboot first, see above.

With the 18.06 merger of openwrt/LEDE and the addition of the Unsorted Block Images (UBI) code to the Mikrotik code base described here Introduce sysupgrade + 64MB/Large NAND sysupgrade images, this has become much simpler than previous versions of openwrt installation.

After loading the initramfs-lzma.elf image using netboot, connect to any of the LAN ports (ether2 through ether9) on the RB493G, login to LUCI (default at, and perform a 'Flash image' from System→Backup/Flash Firmware using the nand-large-squashfs-sysupgrade.bin file.

The other .bin files in the openwrt releases folder, such as this 18.06.1 folder http://downloads.openwrt.org/releases/18.06.1/targets/ar71xx/mikrotik/, are NOT used for the RB493G: use only the nand-large version for the RB493G, which includes support for any optional (current, 2018) WiFi cards.

There is no need to explicitly erase the flash as indicated in prior instructions here and wget2nand has been deprecated with this new release: the sysupgrade .bin file used by 'Flash image' in LuCI handles all these flash details now.

Use the built-in openwrt 'Flash image' in the OpenWrt LuCI web interface to upgrade OpenWRT as indicated in the Permanent Installation guide above. With this latest version of OpenWrt, the same sysupgrade .bin file and procedure is used for the initial flash installation into NAND or subsequent upgrades.

Providing tftp boot and images with an existing openwrt router

On the existing openwrt router

File /etc/config/dhcp

config dnsmasq
        option 'enable_tftp' '1'
        option 'tftp_root' '/tmp/tftpboot/'

config 'boot' 'pxe_mikrotik_rb493g'
        option 'filename' 'vmlinux'
        option 'servername' 'routersetup'
        option 'serveraddress' ''

config 'host' 'mikrotik'
        option 'name'   'mikrotik'
        option 'mac'    '<the ip address of the eth1 port on the mikrotik> You can find it from the mikrotik winbox interface'
        option 'ip'     ''

config dhcp 'lan'
        option interface 'lanmikrotik'
        option start '10'
        option limit '150'
        option leasetime '10m'


File /etc/config/network


config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.0'
        option proto 'static'
        option ipaddr ''
        option netmask ''

config interface 'lanmikrotik'
        option ifname 'br-lan' #it is an alias interface
        option proto 'static'
        option ipaddr ''
        option netmask ''

We need to provide files. Therefore:

cd /tmp/
mkdir tftpboot
wget 'http://downloads.openwrt.org/releases/18.06.1/targets/ar71xx/mikrotik/openwrt-18.06.1-ar71xx-mikrotik-vmlinux-initramfs-lzma.elf'
#this image is needed for booting from the ram

ln -s openwrt-18.06.1-ar71xx-mikrotik-vmlinux-initramfs-lzma.elf vmlinux
# to match the bootloader requests
  • Connect the eth1 port of the Mikrotik to the lan ports of the openwrt router.
  • Unplug the power cable of the Mikrotik.
  • With the proper tool press the reset button near the eth1 interface on the Mikrotik and hold it.
  • Plug in the Mikrotik power cable.
  • Wait for the boot of the Mikrotik (careful, if the Mikrotik has a license level 0 won't be possible to boot in this way).
  • After 10-15 seconds from the boot (after the green light extinguishes), release the button.
  • Now connect the port “eth2” on the mikrotik to a proper device, such as a PC. It should show the openwrt interface, reachable on
  • Use SysUpgrade from LUCI to permanently write the nand-large-squashfs-sysupgrade.bin kernel/ubi image into the NAND of the RB493G

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

The default network configuration is:

Interface Name Description Default configuration
br-lan (eth0, eth1.1) LAN
eth1.2 WAN DHCP

The default switch configuration is:

Board Switch Port VLAN Interface
0 CPU 1
Eth5 0 1 1 eth0
Eth2 0 2 1 eth0
Eth3 0 3 1 eth0
Eth4 0 4 1 eth0
0 5 off
1 CPU 1/2
Eth9 1 1 1 eth1.1
Eth6 1 2 1 eth1.1
Eth8 1 3 1 eth1.1
Eth7 1 4 1 eth1.1
Eth1/PoE 1 5 2 eth1.2

''/etc/config/network'' every port usable as single port

config interface 'loopback'
	     option ifname 'lo'
	     option proto 'static'
	     option ipaddr ''
	     option netmask ''

config switch
	     option name 'switch0'
	     option reset '1'
	     option enable_vlan '1'

# eth5
config switch_vlan
	     option device 'switch0'
	     option vlan '1'
	     option ports '0t 1'

# eth2
config switch_vlan
        option device 'switch0'
        option vlan '2'
        option ports '0t 2'

# eth3
config switch_vlan
        option device 'switch0'
        option vlan '3'
        option ports '0t 3'

# eth4
config switch_vlan
        option device 'switch0'
        option vlan '4'
        option ports '0t 4'

config switch
	      option name 'switch1'
	      option reset '1'
	      option enable_vlan '1'

# eth9
config switch_vlan
	      option device 'switch1'
	      option vlan '1'
	      option ports '0t 1'

# eth6
config switch_vlan
        option device 'switch1'
        option vlan '2'
        option ports '0t 2'

# eth8
config switch_vlan
        option device 'switch1'
        option vlan '3'
        option ports '0t 3'

# eth7
config switch_vlan
        option device 'switch1'
        option vlan '4'
        option ports '0t 4'

# eth1
config switch_vlan
        option device 'switch1'
        option vlan '5'
        option ports '0t 5'

hardware.button on howto use and configure the hardware button(s).

The Routerboard 493G has one software reset button.

Reset reset

The SD-card reader is now supposed to work, but the needed patch is currently not in trunk. You will find the ticket with history here: https://dev.openwrt.org/ticket/12349

Hence precompiled images with working SD-card reader is not yet available from the OpenWrt server. Until that is resolved, you can find compiled kernel and rootfs here: http://ubuntuone.com/1bZTk4vlKwroZezcdeJa4l http://ubuntuone.com/2V1BoearwvvMOsNzUz7mcx

Provide them on a web-server, or copy them manually over to the kernel and rootfs partitions on the nand.

The USB-port of the RB493G is a shameful chapter of Mikrotik engineering.

The USB-standard demands a 5VDC-power-supply on the USB-socket, but Mikrotik tried to save a few cents for a voltage converter. So one has to buy a power-injector from Mikrotik and any 5VDC-power-supply. Pray the plug of your power-supply fits into the power-injector! Just using a powered USB-hub doesn't solve the problem, as USB-hubs only enumerate/register with the host-controller when 5VDC is supplied by the host-controller.

Reliable vendors just update their PCB-layout, but Mikrotik sells that non-standard/sub-standard PCB-layout for years, now.

The Routerboard has a OHCI-controller for USB 1.x and a EHCI-controller for USB 2.0.

See usb-installing for configuration.

Architecture MIPS-BE
Vendor Mikrotik / Qualcomm Atheros
bootloader MikroTik RouterBoot (Rescue- and Main-Bootloader)
Default Operating System MikroTik RouterOS v4, Level5-license
System-On-Chip Atheros AR7161 rev 2
CPU/Speed MIPS 24Kc rev 00019374 680/800 MHz
Flash-Chip Samsung NAND 128MiB 3,3V 8-bit or
ST Micro NAND 01GW3B2CN6 or
Toshiba NAND 128MiB 3,3V 8-bit
Flash size 128 MiB NAND-Flash
Micro-SD 1x Micro-SD-socket (probably SPI)
Wireless optional via 3x Mini-PCI IIIA/B
Ethernet 9x 10/100/1000Base-T(X) (2x Atheros AR8316-5-port-switch with VLAN support swconfig
Internet n/a/xDSL/DOCSIS/3g/LTE
USB 1x 2.0 (unpowered)
Serial YES 1x Sub-DB9 RS-232C asynchronous
JTAG Maybe (contatcs on PCB, not tested)
LED Power, NAND activity, 5x user LED
Power options 10..28 VDC Power-over-Ethernet or Power-Jack
Power consumption ~3 Watt, up to 10 Watt for MiniPCI-cards, maximum 16 Watt
Dimensions 160 mm x 105 mm, 189 grams

Casing: Mikrotik case CA493 with two N-pigtails and -antennas (antennas are ALFA ARS-N19CW, 2.4GHz 9dBi - pigtails and antennas not included in enclosure package)
Enclosure Mikrotik CA493 - top view with antennas

Casing: Mikrotik CA493 with serial port, Ethernet-port, LEDs and power-connector of Routerboard RB493G
Enclosure Mikrotik CA493 - frontside

Casing: Mikrotik CA493 with two N-pigtails (not included), multi-purpose hole (e.g. N-connector, Swivel-antenna, ...) and ground-screw
Enclosure Mikrotik CA493 - backside

Left/Top: Casing: Mikrotik CA493 with eight Ethernet-ports of Routerboard RB493G
Enclosure Mikrotik CA493 - left side

Right: Casing: Mikrotik CA493 with venting holes
Enclosure Mikrotik CA493 - right side

Bottom: Casing: Mikrotik CA493
Enclosure Mikrotik CA493 - bottom

Casing opened:
Casing: Mikrotik CA493 with two N-pigtails (not included), Routerboard 493G and Routerboard R52nM (Wifi-card)
Enclosure Mikrotik CA493 with PCBs

  • To remove the cover just unscrew the 4 screws (2 left side, two right side)

Main PCB top
Mikrotik Routerboard 493GAH - frontside

  • Power socket
  • 2x LED
  • 1x 1000Base-T with proprietary POE
  • 1x Sub-D9 Serial Port (Console by default)
  • 8x 1000Base-T Port
  • 1x Reset-contacts
  • 2x Atheros AR8316 (under heatsinks)
  • 1x JTAG-contacts
  • 1x USB 2.0 (unpowered)
  • 3x MiniPCI Type IIIA/B
  • 2x RAM SAMSUNG K4H510838G-LCCC
  • 2x regulated Fan-connector 3.3V 500mA
  • 2x regulated Fan connector main voltage 500mA
  • 4x Screw holes

Main PCB bottom
Mikrotik Routerboard 493GAH - backside with microSD slot

  • Flash: ST NAND01GW382CNb
  • Flash: microSD-Socket
  • RAM: 2x SAMSUNG K4H510838G-LCCC

The Routerboard has one serial interface in form of a Sub-D9-socket. By default it provides a serial console. It can be accessed with a Null-Modem-Cable (115200, 8N1, no handshaking!).

There are seven contacts named “JTAG” between USB- and MiniPCI-Socket, but not tested.


In worst case keep “Reset”-button pressed when powering on the Routerboard to access the recovery-boot-loader via serial console. That way the Routerboard can be re-flashed with a RouterOS-image (NPK-file) using the origin MikroTik-Netinstall-software (BOOTP/TFTP).

As a beginner, you really should inform yourself about soldering in general and then even obtain some experience!


1x PCB
1x USB-2.0-dual-A-socket, e.g., these.
1x USB-2.0- A-plug, e.g., these.
1x Traco TSR 1-2450 step-down-converter 5VDC/1A (doesn't need any other components like capacitors or heatsink). As of this writing you will find the LM7805V voltage regulator at DealExtreme
1x Multifuse 60VDC/0,5A Ihold/1A Itrip

Proto-type and diagrams/layouts aren't beauties, but maybe someone with more Cadsoft-Eagle-experience can make a nice circuit-diagram and a real PCB-layout: Eagle files and datasheets ;-)

Rudimentary circuit-diagram with USB-2.0 data-port (1) and generic USB-2.0 charger port (2), both supplied by a step-down-converter via the fan-connector of the RB493G:

Rudimentary PCB-layout, not applicable:

USB-mod prototype top-view:

USB-mod prototype bottom-view:

USB-mod prototype attached:

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  • Last modified: 2024/02/12 08:58
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