DHCP client starts flipping connected/disconnected

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi,
I have successfully setup a restricted subnet iot.
This means OpenWrt router rejects egress and ingress on this interface, but specific traffic rules allow DNS, DHCP and NTP.

One of my DHCP clients is a Sony Bravia SmartTV, and this device starts flipping status connected/disconnected.
I can observe on this TV that it fails to identify an internet connection.
And this could be related to my restricted DNS setup, means there's a Pihole server in my network that replies to all DNS requests.

Other clients, e.g. Android smartphone, works w/o issues connected to the same subnet iot.

Could you please advise how to trouble-shoot this issue?

THX

2

Run tcpdump, if that does not help enable network traces on tv.

3

you're asking us why your (non openwrt) pi-hole/DNS is blocking your (non openwrt) TV, and how to fix it ?

1 Like
4

Which tcpdump command options are adviseable?
And how should I enable network tracing on GoogleTV?

5

One google query to rule them all.

6

Look, the issue is a little more complext.
If I disable DHCP on OpenWrt router's iot interface and enable DHCP on another server, this device works w/o problems.
My conclusion is that Pihole is not the root cause.

7

Please spend some time with tcpdump. Pointing fingers at everybody will not convince them to help you. Openwrt as mitm is a goodplace to start, probably pihole next.

Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:
grafik
Remember to redact passwords, MAC addresses and any public IP addresses you may have:

ubus call system board
cat /etc/config/network
cat /etc/config/wireless #if applicable
cat /etc/config/dhcp
cat /etc/config/firewall
8

If you're blocking all output on a zone you need to add an exception for UDP 68 to allow DHCP (v4) renewals. It is safe to allow output by default on a guest/iot network since that would only be connections initiated by the router not the untrusted devices.

2 Likes
9

After modifying DHCP settings this device works as exptected.
Originally I had a DHCP IP range 192.168.1.100-249, and the device received IP 192.168.1.205.
Now this IP range is 192.168.1.100-199.

Maybe this information helps other users with a similar issue.

10

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