[Dnsmasq-discuss] DHCP server not assigning IP to RTMU86

[Geert Stappers]

On Tue, May 17, 2022 at 11:16:28AM +0200, Kamil via Dnsmasq-discuss wrote:
> On Mon, May 16, 2022 at 04:56:25PM +0100, Simon Kelley wrote:
> > On 15/05/2022 15:40, Kamil via Dnsmasq-discuss wrote:
> > > On Sun, May 15, 2022 at 07:21:47AM +0200, Geert Stappers via Dnsmasq-discuss wrote:
> > > > What proof is available of
> > > > the RTMU86 sending DHCP packages
> > > > when pluging the ethercable back in?
 
> > > 16:17:31.125779 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:XX:XX:XX:XX:1c (oui Unknown), length 300

> > > PS. I've read in FAQ about 255.255.255.255 broadcast and invalid
> > > firewall rules, but I don't have any firewall rules and I'm not changing
> > > network config files when switching to isc-dhcp-server (which I use as a
> > > benchmark)
> > >
> >
> > ISC dhcpd bypasses the firewall rules to receive that sort of broadcast
> > packet and dnsmasq doesn't, so the fact that it works with ISC and not
> > with dnsmasq is a strong hint that a firewall rule dropping destination
> > 255.255.255.255 and/or source 0.0.0.0 may well be the problem.
> >
> > What does the output of
> >
> >    iptables -L
> >
> > look like?
> >
> # iptables -L
> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination
>
> Chain FORWARD (policy ACCEPT)
> target     prot opt source               destination
>
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination

Acknowledge on those firewall (empty) rules.


It is still an interesting problem. (Dnsmasq not doing it's DHCP server
task, on same hardware another DHCP server works for an unknown reason.)


I suggest that original poster, the main stakeholder of this challenge,
takes a deeper dive into it. Tooling for that is a network sniffer.
Sniff close to the RTMU86. Start with analyzing the working configuration.


Groeten
Geert Stappers

P.S.  @Kamil:  Your email client doesn't add
  On <timestamp>,  <person>  wrote:
line on top of your responses.

P.S.  @all: Please avoid obfuscation of what you send.
(Please do not mangle MAC addresses)
-- 
Silence is hard to parse