Can't access to DHCP clients on eth0

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1

Hi guys, this might be simple (or not) but I'm not really an advanced network guy, so this is my first time with Pi-Hole, not sure if the application is mostly ideal for pi-hole but let's see.
Context: I've a Raspberry 4 on a remote site, connected to a 4G Router through wlan0. And Pi-Hole is running in the raspberry itself, with a DHCP Server running for ethernet port (eth0). Seems that DHCP Server runs fine since clients gets IP. I'm doing this to request some data of the machine connected to eth0 as client through SNMP.

I connect remotely to the raspberry through AnyDesk. What I expect is to communicate from the Raspberry itself to the DHCP clients from the PI-Hole server. The machine I want to reach gets an IP which is 192.168.0.240 but, for some reason, if I ping the machine it doesn't reach it, BUT, if I run:
ping -I eth0 192.168.0.240
it gets a response. So, for some reason I think the lan clients on eth0 aren't reachable by system. Is there any way to make It system wide accesible? I've been reading that maybe forwarding or something might be the answer.

I also tried to access to that IP from my computer but it's not reachable, I guess of course it won't reach since the raspberry can't access to it itself.

The machine has a web server on port 80, so it would be also great to access to it. Any ideas?
Would be much appreciated.
Thanks in advance

Debug Token:
https://pastebin.com/brHadYEH

2

What does ip route and ip route get 192.168.0.240 show?

3

Hey, thanks for helping me. It drops this

pi@advanceopc3:~ $ ip route
default via 192.168.0.1 dev wlan0 proto dhcp src 192.168.0.103 metric 2 
default via 192.168.0.179 dev eth0 src 192.168.0.22 metric 202 
default via 192.168.0.1 dev eth1 proto dhcp src 192.168.0.179 metric 204 
192.168.0.0/24 dev wlan0 proto dhcp scope link src 192.168.0.103 metric 2 
192.168.0.0/24 dev eth0 proto dhcp scope link src 192.168.0.22 metric 202 
192.168.0.0/24 dev eth1 proto dhcp scope link src 192.168.0.179 metric 204 
pi@advanceopc3:~ $ ip route get 192.168.0.240
192.168.0.240 dev wlan0 src 192.168.0.103 uid 1000 
    cache
4

Your routing shows that you have three different interfaces on your Pi.

  1. wlan0
  2. eth0
  3. eth1

You're using the same network subnet on all three of them, 192.168.0.0/24, which is a networking topology that will cause confusion unless you have a specific need and the requisite routing protocol designed for a multi-homed server. Your output shows that wlan0 is the most preferred interface:

192.168.0.0/24 dev wlan0 proto dhcp scope link src 192.168.0.103 metric 2

The lowest metric count is the one that that will be used if the interface is up.

192.168.0.0/24 dev eth0 proto dhcp scope link src 192.168.0.22 metric 202 
192.168.0.0/24 dev eth1 proto dhcp scope link src 192.168.0.179 metric 204

Next eth0 will be used followed by eth1. (metric 202 and 204 respectively).

The ip route get shows this is the case, traffic to 192.168.0.240 will be sent through wlan0 with the source address of 192.168.0.103.

Easiest solution would be to use separate subnets for each network segment. Or change the routing metrics to prioritize the interface you want to use.

5

Ok, yeah I realize your point. Can't really change metrics since wlan0 connects the raspberry to the internet, if I let the metrics as default raspberry loses internet connection since eth0 hasn't.
I've been trying to change the subnet on the wlan router but can't get the password. I'm about to try to reconfigure Pihole to a different subnet.

Thanks in advance, that should fix the problem since I did some test about that today at home. Going to site tomorrow and I'll try and report. Thanks!!

6

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