DietPi, On RPi4, HiJacking DCHP?!

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fr4nk1yn
Posts: 7
Joined: Mon Mar 25, 2019 1:21 am

DietPi, On RPi4, HiJacking DCHP?!

Post by fr4nk1yn »

This has been happening on and off for awhile. It's gotten worst lately.

Basically my Wi-Fi goes down I'm assuming because the RPi4 taking over DCHP. The access point, 2 different ones, stops giving IP addresses. Unplugging the RPi4 immediatly fixes the issue until it happens again. I can only assume it's trying to take over DCHP responsibilities.

The RPi4 is configured with only what's needed to operate as a "seedbox"/media server with Plex. Ideas on this?
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Joulinar
Posts: 2566
Joined: Sat Nov 16, 2019 12:49 am

Re: DietPi, On RPi4, HiJacking DCHP?!

Post by Joulinar »

Hi,
DietPi, On RPi4, HiJacking DCHP
this basically is not possible, as long as you did not configured or installed any DHCP Server software. By default there is no DHCP server package available on DietPi.
The access point, 2 different ones, stops giving IP addresses
This I don't understand at all. Does it mean you have 2 other devices acting as DHCP Server?

To check who is DCP server on your local network, you coould try the following.

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nmap --script broadcast-dhcp-discover -e eth0
If nmap is not available, it can be installed quite easily

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G_AGI nmap
As well you can try to find out if there is a DHCP server running on your system by checking the LISTEN ports. The server runs on 67/udp, and the client agent runs on 68/udp.

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ss -lp|grep udp
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team
fr4nk1yn
Posts: 7
Joined: Mon Mar 25, 2019 1:21 am

Re: DietPi, On RPi4, HiJacking DCHP?!

Post by fr4nk1yn »

I've had 2 different routers at different times. I've definitely not configured the media server with anything besides what's needed so I wasn't expecting it to take over DCHP. It's just a guess since everything on the network loses their IP addresses until the RPi4 is unplugged, then they instantly get their addresses and connect.

It's an odd one for sure.
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Joulinar
Posts: 2566
Joined: Sat Nov 16, 2019 12:49 am

Re: DietPi, On RPi4, HiJacking DCHP?!

Post by Joulinar »

Hi,

just to avoid a misunderstanding. DHCP server is nothing that can be taken over by someone. DHCP server is a functionality that will be provided by a server device if enabled or not if disabled. Theoretically it can be active on 2 or more server at the same time and it is nothing that can be hijacked. Means if your RPi would be a DHCP Server, it would play this role all the time and not trying to get it from someone else. As I said, you can check LISTEN ports on your RPi to see if it is acting as DHCP Server or DHCP Client
everything on the network loses their IP addresses
What do you mean by this? An IP address is nothing you can loose. It will stay as long as the DHCP lease is active.

Maybe you can configure a Linux based device on your local network with STATIC IP. And if the situation happen that your devices did not get an IP Address assigned (via DHCP), you can logon to that systems and check with the following command if your DHCP request will be answered or not.

Code: Select all

nmap --script broadcast-dhcp-discover -e eth0
Next to that you might need to check if there is an IP Address conflict between your DHCP Server and your RPi. Maybe both are using the same address leading to some network conflicts.
Pls let us know if a solution is working. This could help others if they hit by similar situation. Your DietPi Team
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