[Dnsmasq-discuss] DHCP server not assigning IP to RTMU86
Kamil
kamil at incmachines.com
Mon May 23 18:37:41 UTC 2022
On 20/05/2022 19:19, Simon Kelley <simon at thekelleys.org.uk> wrote:
>
> I have a theory:
>
> In the logs, it takes between 7 and 9 seconds after carrier detect on
> eth0 (I guess that's when you plug the RTMU86 in?) before eth0 is
> allocated IP address 192.168.6.1. Until the address is allocated,
> dnsmasq will ignore DHCP requests and log
>
> "DHCP packet received on eth0 which has no address"
>
> If the RTMU86 send a DHCP discover faster than 7 seconds and doesn't
> retry in a reasonable time, that could explain the problem.
>
> ISC dhcpd may not need the local interface to be configured with an IP
> address, which would explain the different behaviour.
>
>
> The packet capture below shows just one DHCPDISCOVER being sent from
> 0.0.0.0.bootpc > 255.255.255.255.bootps
>
> and it's before the IP 192.168.6.1 > igmp.mcast.net which markswhen
> eth0 gets an IP address.
>
> If you repeat the same test and leave the capture running for a few
> minutes, do you see any more 0.0.0.0.bootpc > 255.255.255.255.bootps
> packets, and if you do, do they get a reply?
>
> If I'm right, the solution may be to configure eth0 with a statis IP
> address, so it doesn't have to wait for dhcpcd to go through a lengthy
> process to give it an IP address every time the cable gets plugged in.
>
>
Dear Simon,
1) I've just sent my reply to Geert where I included my full logs with
exact timestamps and my comments. Please have a look:
https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/msg16249.html
2) Because I'm switching between two devices and the address for "Device X"
is being assigned every time - I think that it's not the case of "time".
3) Also I've left RTMU86 for a little bit longer and as you can see it
retries several times.
4) eth0 has static IP configured for all this time. In /etc/dhcpcd.conf I
have:
> interface eth0
> static ip_address=192.168.6.1/24
Kind regards,
Kamil
>
> Simon.
>
>
> On 15/05/2022 15:40, Kamil via Dnsmasq-discuss wrote:
> >
> > On Sun, May 15, 2022 at 01:10:40AM +0200, Kamil via Dnsmasq-discuss
> > wrote:
> > > On Sat, May 14, 2022 at 11:27:34AM +0200, Geert Stappers via
> > Dnsmasq-discuss wrote:
> > > > On Sat, May 14, 2022 at 02:53:51AM +0200, Kamil via
> > Dnsmasq-discuss wrote:
> > ...
> > > > > 1. I plug one device - it works.
> > > > > 2. I unplug it and plug the RTMU86 - doesn't work.
> > > > > 3. I Unplug RTMU86 and plug any other device - it works.
> > > > >
> > ...
> > > > Be yourself, accept yourself. Full focus on the challenge that
> > you are
> > > > facing.
> > >
> > > Sure
> > >
> >
> > What proof is available of
> > the RTMU86 sending DHCP packages
> > when pluging the ethercable back in?
> >
> >
> > RTMU86 has a led indicator that is lid when the address has been
> > assigned to it.
> > 1. If I plug RTMU86 to the home router - the led is on, I can find its
> > IP in the router's lease list and I can ping this IP
> > 2. If I plug RTMU86 to the RPi with isc-dhcp-server configured - the led
> > is on, I can find its IP in the isc-dhcp-server's lease list and I can
> > ping this IP
> > 3. If I plug RTMU86 to the RPi with Dnsmasq configured - I can use
> > tcpdump which gives me this output (I changed MAC addresses):
> > > 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
> > So I presume that RTMU86 indeed sends DHCP packages, but the led is off
> > and I can not find it in the Dnsmasq lease list.
> >
> > Full tcpdump log (with changed MAC addresses) below:
> > > 16:17:28.175124 IP6 :: > ff02::16: HBH ICMP6, multicast listener
> > report v2, 2 group record(s), length 48
> > > 16:17:28.187120 IP6 :: > ff02::16: HBH ICMP6, multicast listener
> > report v2, 4 group record(s), length 88
> > > 16:17:28.199412 ARP, Request who-has 192.168.6.1 tell 0.0.0.0, length
> 28
> > > 16:17:28.235076 IP6 :: > ff02::16: HBH ICMP6, multicast listener
> > report v2, 4 group record(s), length 88
> > > 16:17:28.483118 IP6 :: > ff02::1:fffb:fe9: ICMP6, neighbor
> > solicitation, who has fe80::XX:XX:XX:fe9, length 32
> > > 16:17:29.507285 IP6 fe80::XX:XX:XX:fe9 > ff02::16: HBH ICMP6,
> > multicast listener report v2, 5 group record(s), length 108
> > > 16:17:29.507966 IP6 fe80::XX:XX:XX:fe9 > ip6-allrouters: ICMP6,
> > router solicitation, length 16
> > > 16:17:29.519049 IP6 fe80::XX:XX:XX:fe9 > ff02::16: HBH ICMP6,
> > multicast listener report v2, 1 group record(s), length 28
> > > 16:17:29.891065 IP6 fe80::XX:XX:XX:fe9 > ff02::16: HBH ICMP6,
> > multicast listener report v2, 5 group record(s), length 108
> > > 16:17:30.019064 IP6 fe80::XX:XX:XX:fe9 > ff02::16: HBH ICMP6,
> > multicast listener report v2, 1 group record(s), length 28
> > > 16:17:30.077265 IP6 fe80::XX:XX:XX:fe9.mdns > ff02::fb.mdns: 0*- [0q]
> > 2/0/0 (Cache flush) PTR myhost.local., (Cache flush) AAAA
> > fe80::XX:XX:XX:fe9 (139)
> > > 16:17:30.151935 ARP, Request who-has 192.168.6.1 tell 0.0.0.0, length
> 28
> > > 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
> > > 16:17:31.728625 ARP, Request who-has 192.168.6.1 tell 0.0.0.0, length
> 28
> > > 16:17:32.152301 IP6 fe80::XX:XX:XX:fe9.mdns > ff02::fb.mdns: 0*- [0q]
> > 2/0/0 (Cache flush) PTR myhost.local., (Cache flush) AAAA
> > fe80::XX:XX:XX:fe9 (139)
> > > 16:17:33.510623 IP6 fe80::XX:XX:XX:fe9 > ip6-allrouters: ICMP6,
> > router solicitation, length 16
> > > 16:17:33.730051 ARP, Request who-has 192.168.6.1 tell 192.168.6.1,
> > length 28
> > > 16:17:33.739141 IP 192.168.6.1 > igmp.mcast.net
> > <http://igmp.mcast.net>: igmp v3 report, 1 group record(s)
> >
> > 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)
> >
> > Kind regards,
> > Kamil
> >
> >
> >
> > Groeten
> > Geert Stappers
> > --
> > Silence is hard to parse
> >
> > _______________________________________________
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> >
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> >
> >
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