OpenWrt will not install on Mikrotik RB760igs, tried everything

[freddy]

Hello,

since hours I'm trying to install openwrt on that damnet Mikrotik garbage

Mikrotik RB760igs

I'm using Windows 10 64bit

I tried it with tinyPXE and TFTPD but without any success. After hours of changing configurations, network cables, USB ethernet cards, ... I get the following now:
"Got IP address: 192.168.1.12"
"resolved mac address 00:50:B6:0A:B3:A8"
"**********************falling back to small packet size"
"**********************kernel loading failed"

Files I'm trying to use:
openwrt-ramips-mt7621-mikrotik_routerboard-760igs-initramfs-kernel.bin
openwrt-ramips-mt7621-mikrotik_routerboard-760igs-squashfs-sysupgrade.bin

Current router settings:
o-e "boot device - boot over Ethernet"
p-1 "boot protocol - bootp protocol"
b-2 "booter options - force backup-booter loading"
but I tried all combinations of these three settings...

Any idea what could be the problem here?

[lleachii]

@freddy, welcome to the commnity!

@freddy

Any idea what could be the problem here?

• Do you have to enable TFTP on the MikroTik?
  • Did you do so?
• Did you open the firewall on the Windows mahcine?

[mk24]

I don't see much instructions about the RB760igs offhand. I do see that you're trying to PXE network boot, but options 66 and 67 are not set. If it's doing a full PXE boot your DHCP server has to send option 66 to point the router at the TFTP server-- which in this case is also the Windows PC. Option 67 is probably also needed for the file name. Rename the initramfs to a short name and check the TFTP server to see if any file was requested.

Use initramfs for network boot then the sysupgrade is the second step to install.

[freddy]

First of all, thanks a lot for your tips!

I don't know why, just changed the bootloader settings arround, switched over to TFTPD again, changed back to the settings mentioned above. While the router was trying to connect I stopped TFTPD and started tinyPXE again and now it's working

Years ago I installed OpenWrt on several WRT54g and also on an Asus RT-N10U, never had lot of bad experiences but this thing drove me nearly crazy

Maybe anybody can give me a hint what's the meaning of that ***** the router shows, because now since it's working I get:
"transfer started ................................... transfer ok, time=3.72"

[tmomas]

If your problem is solved, please consider marking this topic as [Solved]. See How to mark a topic as [Solved] for a short how-to.

[freddy]

Here is what I did so far to get the router working

Uninstall personal firewall stuff and virus scanner, it's recommended to do this inside a virtual machine

Select correct files for RB760igs from OpenWrt page

Open device and solder serial terminal (e.g. use CH340 to USB module), this will save you a lot of time but you will lose warranty!

Press "x" on terminal to enter bootloader menu

enter p-1     = bootp
enter o-e     = boot from Ethernet (must be changed later!)
enter b-2     = force backup-bootloader loading
enter e-yes   = format storage (no fear, can be undone with Mikrotiks netinstall tool)

If you have problems with the network

try another cable
try another USB-Ethernet card

Set your network card to

IPv4    192.168.1.2
Subnet  255.255.255.0
gateway 192.168.1.1

Use TinyPXE

copy image "...initramfs..." into TinyPXE sub folder .../file/boot
select "HTTPd"
set Option 54 to        192.168.1.2
set IP Pool start to    192.168.1.3
set Next-Server to      192.168.1.2
set Option 1 to         255.255.255.0
set Option 3 to         192.168.1.1
set Option 6 to         192.168.1.1
set Option 28 to        192.168.1.255
enter the "...initramfs..." file into Filename text field
deselect "Filename if user-class=gPXE or iPXE"
select [Online]

Now let the router boot...

Router should boot with following message (or similar one)

RouterBOOT backup booter 6.46.3

RB760iGS

CPU frequency: 880 MHz
Memory size: 256 MiB
Storage size:  16 MiB

Press any key within 2 seconds to enter setup..

loading kernel... kernel not found
trying bootp protocol.... OK
Got IP address: 192.168.1.13
resolved mac address 00:50:B6:0A:B3:A8
transfer started ................................... transfer ok, time=4.44s
setting up elf image... OK
jumping to kernel code
[    0.000000] Linux version 5.4.81 (builder@buildhost) (gcc version 8.4.0 (OpenWrt GCC 8.4.0 r15151-13961da6ce)) #0 SMP Sun Dec 6 08:18:07 2020
...

Copy "...sysupgrade..." file to router via scp

scp -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null openwrt-ramips-mt7621-mikrotik_routerboard-760igs-squashfs-sysupgrade.bin root@192.168.1.1:/tmp

Write image into NAND flash now

sysupgrade -v /tmp/openwrt-ramips-mt7621-mikrotik_routerboard-760igs-squashfs-sysupgrade.bin

Connect the router's WAN port to your common router and reset it to get internet access

opkg update
opkg install luci-ssl
opkg install luci-i18n-base-<language>

Hope this helps anybody, otherwise please ignore it!