On 18/05/2021 20:57, Geert Stappers wrote:
On Fri, May 14, 2021 at 08:30:42AM +0100, Nick Howitt wrote:
On 13/05/2021 22:30, Geert Stappers via Dnsmasq-discuss wrote:
On Thu, May 13, 2021 at 09:31:21PM +0100, Nick Howitt wrote:
On 13/05/2021 19:26, Geert Stappers via Dnsmasq-discuss wrote:
On Thu, May 13, 2021 at 01:05:07PM +0100, Nick Howitt wrote:
I am trying to help someone who has a set up with three LAN's, all on
different subnets and all acting as DHCP servers. He is getting an odd
result that when a device on the enp2s0 LAN requests an IP, both enp2s0 and
enp3s0 respond with IP's. I've never seen this before and my own server does
not act this way.
...
From the dnsmasq log:
May 8 11:23:39 dnsmasq-dhcp[7226]: DHCPDISCOVER(enp2s0) de:ad:c0:de:ca:fe
May 8 11:23:39 dnsmasq-dhcp[7226]: DHCPOFFER(enp2s0) 192.168.1.214
de:ad:c0:de:ca:fe
May 8 11:23:42 dnsmasq-dhcp[7226]: DHCPDISCOVER(enp3s0) de:ad:c0:de:ca:fe
May 8 11:23:42 dnsmasq-dhcp[7226]: DHCPOFFER(enp3s0) 192.168.168.215
de:ad:c0:de:ca:fe
...
I have a similar dual LAN set up and it works as expected with each
LAN only responding with its own LAN DHCP settings.
That means the "problem" is outside dnsmasq.
Thanks,
Feel welcome to report back.
OK, but if the problem is outside dnsmasq, why does dnsmasq log two
DHCPDISCOVERs and DHCPOFFERs? Could he have a networking problem with the
two LAN's bridged somewhere?
Yes
Perhaps I can ask him to unplug the cable to
enp3s0 and see if the problem goes away.
It is surely an usefull trouble shoot check.
or perhaps less intrusive is two ssh sessions running:
tcpdump -nni enp2s0 '(ether host de:ad:c0:de:ca:fe and port 67)'
and:
tcpdump -nni enp3s0 '(ether host de:ad:c0:de:ca:fe and port 67)'
Then try the nmap test. If both sessions respond, then there is a bridge.
And how did go?
Groeten
Geert Stappers
P.S.
FWIW for the two SSH sessions would I use one session.
In that session `tmux` and the screen split horizontal.
He was not going to get to the site until today to check. I will let you
know as soon as I find out. I am intrigued as well. tmux is a new one
for me!
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