The most obvious explanation for this is that the two LANs in question have becomes bridged together at level 2.
Simon. On 13/05/2021 13:05, 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 an nmap scan from a device on the enp2s0 LAN: > ubuntu-local@latitude-e7470:~$ sudo nmap > --script=broadcast-dhcp-discover -e enp0s31f6 > Starting Nmap 7.91 ( https://nmap.org <https://nmap.org> ) at 2021-05-08 > 11:23 EDT > Pre-scan script results: > | broadcast-dhcp-discover: > | Response 1 of 2: > | Interface: enp0s31f6 > | IP Offered: 192.168.1.214 > | DHCP Message Type: DHCPOFFER > | Server Identifier: 192.168.1.1 > | IP Address Lease Time: 2m00s > | Renewal Time Value: 1m00s > | Rebinding Time Value: 1m45s > | Domain Name: emdentalb.local > | Domain Name Server: 192.168.1.1 > | Router: 192.168.1.1 > | Broadcast Address: 192.168.1.255 > | Subnet Mask: 255.255.255.0 > | Response 2 of 2: > | Interface: enp0s31f6 > | IP Offered: 192.168.168.215 > | DHCP Message Type: DHCPOFFER > | Server Identifier: 192.168.168.1 > | IP Address Lease Time: 2m00s > | Renewal Time Value: 1m00s > | Rebinding Time Value: 1m45s > | Domain Name: emdentalb.local > | Domain Name Server: 192.168.168.1 > | Router: 192.168.168.1 > | Broadcast Address: 192.168.168.255 > |_ Subnet Mask: 255.255.255.0 > WARNING: No targets were specified, so 0 hosts scanned. > Nmap done: 0 IP addresses (0 hosts up) scanned in 10.29 seconds > > 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 > > His current configs (so not at the time of the logs as they have been > tweaked to troubleshoot): > /etc/dnsmasq.conf: > bogus-priv > cache-size=5000 > conf-dir=/etc/dnsmasq.d > dhcp-authoritative > dhcp-lease-max=1000 > domain-needed > domain=######.local > expand-hosts > log-facility=/var/log/dnsmasq > no-negcache > port=53 > read-ethers > resolv-file=/etc/resolv-peerdns.conf > strict-order > user=nobody > > /etc/dnsmasq.d/dhcp.conf: > dhcp-option=enp2s0,1,255.255.255.0 > dhcp-option=enp2s0,28,192.168.1.255 > dhcp-option=enp2s0,3,192.168.1.1 > dhcp-option=enp2s0,6,192.168.1.250 > dhcp-option=enp3s0,1,255.255.255.0 > dhcp-option=enp3s0,28,192.168.168.255 > dhcp-option=enp3s0,3,192.168.168.1 > dhcp-option=enp3s0,6,192.168.1.1,192.168.168.1 > dhcp-option=enp4s0,1,255.255.255.0 > dhcp-option=enp4s0,28,192.168.169.255 > dhcp-option=enp4s0,3,192.168.169.1 > dhcp-option=enp4s0,6,192.168.169.1 > dhcp-range=enp2s0,192.168.1.100,192.168.1.199,infinite > dhcp-range=enp3s0,192.168.168.50,192.168.168.99,48h > dhcp-range=enp4s0,192.168.169.100,192.168.169.254,24h > > The infinite leases was an attempt to get round the problem as the > devices were picking up IP's from the wrong LAN. > > Do you know what is wrong here? How can I troubleshoot? I have a similar > dual LAN set up and it works as expected with each LAN only responding > with its own LAN DHCP settings. Both of us are running > dnsmasq-2.76-10.el7_7.1.x86_64. > > Thanks, > Nick > > > > _______________________________________________ > Dnsmasq-discuss mailing list > Dnsmasq-discuss@lists.thekelleys.org.uk > https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
