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. -- Silence is hard to parse _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
