Install OpenWrt on the ASUS RT-AX52 and monitor it via SNMP

1. Connect and log in

Connect your PC to one of the Asus's LAN ports (NOT the WAN/Internet port — a classic pitfall, the WAN port isn't bridged to the admin interface).

Go to http://192.168.50.1 in your browser, work through the QIS setup wizard, and set an admin password. The wireless setup step in the wizard doesn't matter here (it will be overwritten later) — enter anything.

Plugged the cable into the wrong port (WAN)? The router still answers physically (Windows shows "Connected"), but nothing responds at the IP level — neither 192.168.50.1 nor later 192.168.1.1. Move the cable to one of the numbered LAN ports.

2. Trampoline-flash to OpenWrt (snapshot)

Download: openwrt-mediatek-filogic-asus_rt-ax52-initramfs.trx from downloads.openwrt.org/snapshots/targets/mediatek/filogic/

Upload it via Administration → Firmware Upgrade in the ASUS GUI (http://192.168.50.1/Advanced_FirmwareUpgrade_Content.asp). The wizard's own upload shortcut may reject the file ("Invalid file format or path") due to an overly strict filename check — use the full admin page if that happens.

Wait 2-4 minutes while it flashes and reboots.

3. Reaching OpenWrt

OpenWrt's default LAN IP is 192.168.1.1. Set a static IP on your PC's ethernet connection in the same subnet (e.g. 192.168.1.2/24, no gateway).

Is your PC also on wifi in the same 192.168.1.x subnet (e.g. another router with the same default IP)? Windows can't tell "same IP, two physical devices" apart — turn wifi off temporarily, or you'll end up talking to the wrong device.

4. Hop to stable OpenWrt

Download: openwrt-24.10.3-mediatek-filogic-asus_rt-ax52-squashfs-sysupgrade.bin from downloads.openwrt.org/releases/24.10.3/targets/mediatek/filogic/

Transfer and flash:

scp -O openwrt-24.10.3-mediatek-filogic-asus_rt-ax52-squashfs-sysupgrade.bin root@192.168.1.1:/tmp/
ssh root@192.168.1.1
sysupgrade -v /tmp/openwrt-24.10.3-mediatek-filogic-asus_rt-ax52-squashfs-sysupgrade.bin

-O is required — OpenWrt's minimal SSH lacks sftp-server, which newer Windows scp otherwise expects. The connection drops mid-reboot — that's normal.

5. After the upgrade

Set a root password immediately in LuCI (http://192.168.1.1) — the "no password set" warning stays visible until you do.

Change the LAN IP (Network → Interfaces → LAN) to something unique that won't collide with other routers on the same network during setup (e.g. 192.168.5.1) — this avoids routing ambiguity on your management PC. Change it back to the permanent IP (e.g. 192.168.1.1) once the old router is fully retired.

6. Connect WAN and give it a real IP

Move the cable to the WAN port, connect it to your real network/router.

Network → Interfaces → WAN → Static address: IP, netmask, gateway, DNS matching your network setup.

Confirm internet access via Network → Diagnostics (ping an external address, e.g. 8.8.8.8).

7. Install and configure SNMP (including disk usage from the start)

opkg update
opkg install snmpd
uci set snmpd.public.community='YOUR-COMMUNITY-STRING'
uci set snmpd.public6.community='YOUR-COMMUNITY-STRING'
uci add snmpd disk
uci set snmpd.@disk[-1].partition='/'
uci set snmpd.@disk[-1].size='10000'
uci commit snmpd
/etc/init.d/snmpd enable
/etc/init.d/snmpd restart

The disk section is required for disk usage to show up in jegon.net at all — without it, UCD-SNMP-MIB's filesystem table is empty even though everything else works fine (the same trap as on plain Linux — see the "SNMP on Linux (net-snmp)" guide under /snmp/guides/linux).

Test locally:

opkg install snmp-utils
snmpwalk -v2c -c YOUR-COMMUNITY-STRING -O n localhost .1.3.6.1.2.1.1

-O n avoids snmpwalk needing to look up names in MIB files, which aren't installed by default.

8. Open UDP port 161 in the firewall (critical, easy to miss)

SNMP working "locally" (the step above) does not mean Zabbix can reach the device from the outside. OpenWrt's default firewall drops all new incoming connections from the WAN zone by default — including SNMP. Without an explicit rule, the device answers snmpwalk ... localhost just fine, but Zabbix's polling from the internet simply times out with no error message anywhere — a silent trap that's easy to lose a lot of time on.

jegon.net's monitoring always comes from snmp.jegon.net (77.233.252.125). Allow SNMP from that address only, so the router doesn't answer everyone on the internet:

uci add firewall rule
uci set firewall.@rule[-1].name='Allow-SNMP-jegon'
uci set firewall.@rule[-1].src='wan'
uci set firewall.@rule[-1].src_ip='77.233.252.125'
uci set firewall.@rule[-1].proto='udp'
uci set firewall.@rule[-1].dest_port='161'
uci set firewall.@rule[-1].target='ACCEPT'
uci commit firewall
/etc/init.d/firewall restart

OpenWrt's firewall only accepts IP addresses in src_ip, not hostnames — that's why the address is given as a number.

9. Add it in jegon.net

Go to /snmp → add a host with the device's WAN IP + community string, choose the "Wifi Router (Linux) by SNMP" template (OpenWrt reports itself as Linux/net-snmp — the same underlying template as "Linux by SNMP", just with a name that better fits a router).

The disk usage panel can take up to an hour to show up even when everything above was done correctly — Zabbix only discovers the new filesystem item on its next scheduled discovery run, separate from regular metric polling. CPU/memory/load/network usually show up within a minute.

10. See who is on the Wi-Fi (optional)

jegon.net can also show which devices are connected to the router's Wi-Fi, when they come and go, and how much traffic they use. The router only contacts jegon.net when a device connects or disconnects - nothing needs to be opened in the firewall.

Open the router under /snmp in jegon.net, find the "Wi-Fi clients" box and click "Turn on Wi-Fi monitoring". Run the command jegon.net shows on the router. See the guide Wi-Fi clients on an OpenWrt router for details.