Use Zyxel EX3301-T0 as WiFi-router behind OpenWrt

Installing and Using OpenWrt
1

I have OpenWrt running on a Raspberry Pi 4B, connected to the ISP.
Tried to attach a Zyxel EX3301-T0 WiFi-router via Ethernet cable to the Pi.
The Zyxel indicates problems, though. Its red light is ON, and I can't
route packets through the Zyxel.
The IP address of the inner interface of the Pi is 192.168.2.1.
There is an entry for the routing in the Pi:

config route 'route_zyxel'
        option interface 'lan'
        option target '192.168.1.0'
        option netmask '255.255.255.0'
        option gateway '192.168.2.200'

And an entry in the file /etc/config/dhcp:

# Zyxel
config host
       option dns '1'
       option mac 'fc:22:f4:76:bb:03'
       option ip '192.168.2.200'

The IP address of the inner interface (i e not the WAN interface) of the Zyxel router is defined to 192.168.1.1.
I started tcpdump in the Pi, and powered the Zyxel up, which gave the following packets.
(I'm excluding IPv6 packets since I'm only interested in IPv4.)
Is this log enough to tell how the problem could be solved?

14:52:25.464568 IP 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from fc:22:f4:76:bb:03 (oui Unknown), length 548
14:52:25.465477 IP Y.lan.67 > 192.168.2.200.68: BOOTP/DHCP, Reply, length 300
14:52:25.544886 IP 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from fc:22:f4:76:bb:03 (oui Unknown), length 548
14:52:25.546137 IP Y.lan.67 > 192.168.2.200.68: BOOTP/DHCP, Reply, length 300
14:52:30.570484 ARP, Request who-has 192.168.2.200 tell Y.lan, length 28
14:52:31.610450 ARP, Request who-has 192.168.2.200 tell Y.lan, length 28
14:52:32.650445 ARP, Request who-has 192.168.2.200 tell Y.lan, length 28
14:52:34.213805 ARP, Request who-has 192.168.1.1 tell 192.168.1.1, length 46
14:52:34.392958 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:34.653931 ARP, Request who-has Y.lan tell Y.lan, length 46
14:52:34.953084 ARP, Request who-has Y.lan tell Y.lan, length 46
14:52:35.922909 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:36.612884 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:37.602851 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:37.892995 IP Y.lan > 239.255.255.250: igmp v2 report 239.255.255.250
14:52:38.212900 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:47.442778 IP Y.lan > 239.255.255.250: igmp v2 report 239.255.255.250
14:52:50.153334 ARP, Request who-has Y.lan tell Y.lan, length 46
14:52:53.161425 IP Y.lan > all-routers.mcast.net: igmp leave 239.255.255.250
14:52:54.462644 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:52:54.562945 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:52:54.952695 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:53:01.313452 ARP, Request who-has 192.168.1.1 tell 192.168.1.1, length 46
14:53:02.033208 ARP, Request who-has Y.lan tell Y.lan, length 46
14:53:02.343722 ARP, Request who-has Y.lan tell Y.lan, length 46
14:53:03.172619 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:53:03.552517 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:53:03.602543 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:53:03.643585 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:53:04.022469 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:53:04.332781 IP 192.168.2.200 > igmp.mcast.net: igmp v3 report, 1 group record(s)
14:53:08.838066 IP Y.lan.50905 > 239.255.255.250.1900: UDP, length 172
14:53:08.838467 IP Y.lan.52456 > 239.255.255.250.1900: UDP, length 244
etc and many more port 1900-packets from Y.lan...
14:53:08.962538 IP Y.lan > 239.255.255.250: igmp v2 report 239.255.255.250

Y.lan is the Raspberry Pi.

3

Does you Pi have one or two ethernet ports ?

4

The Pi has two Ethernet ports (one real and the other realized via a USB-dongle).
Routing through the Pi works okay to/from another network, 192.168.3.x.

5

So the issue's the EX3301, a device not supported by Openwrt?

6

I believe the issue is the Zyxel EX3301, if I've setup OpenWrt OK.

7

is the netmask ok?
i think it should be 255.255.0.0 as there are two subnet. i am not sure about it just telling. and why there is zero in
option target 192.168.1.0

?

and what about the gateway? shouldn't it be the pi's ip address?

and why do you bother about routing and static dhcp? just remove the config you've made on the pi for wifi/ap and set the 2nd router as dhcp client from the 2nd router's firmware. (this should give a ip address on the same subnet) after success set a static ip from openwrt or leave it.

8

The netmask is alright, I do believe. I have another subnet 192.168.3.x
connected to the Pi, so the netmask should be 255.255.255.0.
Routing through the Pi works to/from that another network, 192.168.3.x and
that makes me assume that static routes have to be defined. 192.168.3.x
has a static route.

option target '192.168.1.0'

defines the network address of the route. Since the first three bytes in the
netmask are 255, and the last byte is 0, I assume that only the first three bytes
in the network address are significant.

The gateway defines where the Pi should route packets with IP addresses that
match 192.168.2.*

Maybe I shouldn't bother about static DHCP. But I have to define the gateway in
the file /etc/config/network.