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BenAlabaster
Asked: 2016-08-12 07:08:24 +0800 CST

How to configure dnsmasq for dhcp with domain names

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I'm playing around with a virtual network inside of VirtualBox 5.0.26 (with Guest Additions). I am using dnsmasq for dhcp and dns and the machines all apear to be allocated their network information correctly, however, I can only ping machines in the network using their hostnames, but not their fully qualified domain names and I can't figure out why.

My VirtualBox has 2 networks configured:

  • NAT Network [10.0.2.0/24], Supports DHCP

  • Host Only Network Adapter [192.168.62.1 / 255.255.255.0], No DHCP

In my Virtual Box network I have a couple of dummy machines: 2 Centos boxes with minimal installs + net-tools, bind-utils and dnsmasq; and an Ubuntu box:

Centos1:

- Minimal Centos 7 install + net-tools, bind-utils, dnsmasq
- /etc/hostname =>
     centos1
- /etc/hosts =>
     127.0.0.1 centos1.mytestnetwork.lab centos1
- /etc/resolv.conf
     # Generated by NetworkManager
     search home.local
     nameserver 10.1.10.10 #IP of legit DNS server
     nameserver 10.1.10.11 #IP of legit DNS server
     nameserver 192.168.62.10
     # NOTE: the lic resolver may not support more than 3 nameservers
     # The nameservers listed below may not be recognized
     nameserver: 127.0.0.1
- /etc/resolv.conf.dnsmasq
     127.0.0.1
- Primary NIC [enp0s3] connected to NAT Network configured for dhcp
- Secondary NIC [enp0s8] connected to Host Only Network with static IP 192.168.162.10

Centos2: 

- Minimal Centos 7 install + net-tools, bind-utils
- /etc/hostname =>
    centos2
- /etc/hosts =>
    127.0.0.1 localhost localhost.localdomain
    ::1       localhost localhost.localdomain
- Primary NIC [enp0s3] connected to NAT Network configured for dhcp
- Secondary NIC [enp0s8] connected to Host Only Network configured for dhcp.

Ubuntu1:

- Ubuntu 14.04 LTS default install with default configuration

On Centos1, the content of my /etc/dnsmasq.conf file is as follows:

resolv-file=/etc/resolve.conf.dnsmasq
bogus-priv
local=/mytestnetwork.lab/
domain=mytestnetwork.lab
interface=enp0s8
no-hosts
addn-hosts=/etc/hosts.dnsmasq
expand-hosts
dhcp-range=192.168.62.50,192.168.62.250,255.255.255.0,24h

Both machines appear to be allocated their IP and domain name correctly from dnsmasq when they boot up, so:

Centos2.MyTestNetwork.lab [192.168.162.51]
Ubuntu1.MyTestNetwork.lab [192.168.162.52]

Both machines are listed in the /var/lib/dnsmasq/dnsmasq.leases file as I would expect.

1471010530 00:00:27:d4:ce:8d 192.168.62.51 centos2 *
1471010650 00:00:27:6d:12:95 192.168.62.52 ubuntu1 *

Checking Centos2 and Ubuntu1's /etc/resolv.conf files, I see Centos1's IP address listed in the nameserver list on both.

If I do an nslookup from either machine using just the host name, and tailing the /sys/log/messages I see the dns request come into dnsmasq, nslookup lists the correct DNS server the IP address is resolved correctly. I can ping using just the hostname.

;; Got SERVFAIL reply from 10.1.10.11, trying next server
;; Got SERVFAIL reply from 10.1.10.10, trying next server
Server:       192.168.62.10
Address:      192.168.62.10#53

Name:   ubuntu1
Address: 192.168.62.52

If however, I do an nslookup using the fqdn, no dns request comes into dnsmasq and the machine cannot be pinged.

Server:       10.1.10.11
Address:      10.1.10.11#53

** server can't find ubuntu1.mytestnetwork.lab: NXDOMAIN

I'm confused why it gives an NXDOMAIN in this case and doesn't try the next server until it finds the IP rather than give up at the first hurdle.

centos domain-name-system virtualbox dnsmasq

1 Answers

  1. I don't know if this is the right answer to this question, but this solution appears to resolve my issue, perhaps someone can comment if there's a better or more correct solution:

    On Centos1, change the primary network card (enp0s3) from DHCP to static IP configuration by editing /etc/sysconfig/network-scripts/ifcfg-enp0s3

    BOOTPROTO=none
ONBOOT="yes"
IPADDR=10.0.2.24
NETMASK=255.255.255.0
GATEWAY=10.0.2.1
DNS1=127.0.0.1
DNS2=10.1.10.11
DNS3=10.1.10.10

    Then sudo systemctl restart network or ifdown enp0s3 and ifup enp0s3

    This in turn modifies my /etc/resolv.conf

    # Generated by NetworkManager
nameserver 127.0.0.1
nameserver 10.1.10.11
nameserver 10.1.10.10

    and I can now remove /etc/resolv.conf.dnsmasq and comment out the reference to it in my /etc/dnsmasq.conf

    I can now ping by fqdn and by hostname alone.

    Ideally, I would like my primary network card to be DHCP... but I can live without it if this is the only way.

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