Nicolas Kovacs
2019-Jan-02 15:09 UTC
[CentOS] Erratic local hostname resolution with Dnsmasq
Hi,
My local server is running CentOS 7. The machine has two NICs and is
acting as a gateway. For DHCP and DNS, I'm using Dnsmasq. I have a
strange little problem with local hostname resolution. Before going into
more details, here's my configuration.
[root at nestor:~] # ifconfig
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255
ether 2c:27:d7:15:54:a1 txqueuelen 1000 (Ethernet)
RX packets 17122 bytes 17596130 (16.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 13426 bytes 2144915 (2.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 18 memory 0xfe8e0000-fe900000
enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.2.1 netmask 255.255.255.0 broadcast 192.168.2.255
ether 00:22:64:8a:4c:c2 txqueuelen 1000 (Ethernet)
RX packets 6597320 bytes 9692134059 (9.0 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 534283 bytes 57365155 (54.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 16 memory 0xfe9e0000-fea00000
[root at nestor:~] # cat /etc/hostname
nestor
[root at nestor:~] # cat /etc/hosts
# /etc/hosts
127.0.0.1 localhost.localdomain localhost
192.168.2.1 nestor.microlinux.lan nestor
192.168.2.252 hp-officejet.microlinux.lan hp-officejet
192.168.2.253 nas.microlinux.lan nas
192.168.2.254 wifi.microlinux.lan wifi
[root at nestor:~] # cat /etc/resolv.conf
# /etc/resolv.conf
nameserver 127.0.0.1
[root at nestor:~] # cat /etc/dnsmasq.conf
# /etc/dnsmasq.conf
domain-needed
bogus-priv
interface=enp3s0
dhcp-range=192.168.2.100,192.168.2.200,24h
local=/microlinux.lan/
domain=microlinux.lan
expand-hosts
# Cloudflare
server=1.1.1.1
server=1.0.0.1
# Google
#server=8.8.8.8
#server=8.8.4.4
no-resolv
# Google
dhcp-host=D4:85:64:B2:B2:1B,alphamule,192.168.2.2
dhcp-host=00:1E:C9:43:A7:BF,bernadette,192.168.2.3
dhcp-host=00:1D:09:15:4A:D8,raymonde,192.168.2.4
dhcp-host=00:1E:C9:42:84:7B,amandine,192.168.2.5
dhcp-host=B8:CA:3A:D6:5A:43,1C:3E:84:32:7E:87,buzz,192.168.2.6
dhcp-host=90:E6:BA:CF:04:8F,64:70:02:9A:AC:93,balthazar,192.168.2.7
dhcp-host=08:00:27:00:00:01,centosbox,192.168.2.10
dhcp-host=08:00:27:00:00:02,susebox,192.168.2.11
dhcp-host=10:62:E5:D4:95:60,hp-officejet,192.168.2.252
dhcp-host=00:11:32:26:63:A5,nas,192.168.2.253
Now here's the problem. Some of the hostname are correctly resolved,
while others are not. Here's what it looks like when invoked from the
server.
[root at nestor:~] # host alphamule
alphamule has address 192.168.2.2
[root at nestor:~] # host bernadette
bernadette has address 192.168.2.3
[root at nestor:~] # host raymonde
Host raymonde not found: 3(NXDOMAIN)
[root at nestor:~] # host amandine
Host amandine not found: 3(NXDOMAIN)
[root at nestor:~] # host buzz
[root at nestor:~] # host balthazar
balthazar has address 192.168.2.7
[root at nestor:~] # host centosbox
Host centosbox not found: 3(NXDOMAIN)
[root at nestor:~] # host susebox
Host susebox not found: 3(NXDOMAIN)
[root at nestor:~] # host hp-officejet
hp-officejet has address 192.168.2.252
[root at nestor:~] # host nas
nas has address 192.168.2.253
Of course I could add all these hosts to /etc/hosts, but as far as I
understand, this *should* work with the hosts appearing only in
/etc/dnsmasq.conf. Or have I overlooked something ? Any suggestions ?
Cheers & happy new year,
Niki
--
Microlinux - Solutions informatiques durables
7, place de l'?glise - 30730 Montpezat
Site : https://www.microlinux.fr
Blog : https://blog.microlinux.fr
Mail : info at microlinux.fr
T?l. : 04 66 63 10 32
Nicolas Kovacs
2019-Jan-02 15:38 UTC
[CentOS] Erratic local hostname resolution with Dnsmasq
Le 02/01/2019 ? 16:09, Nicolas Kovacs a ?crit :> Of course I could add all these hosts to /etc/hosts, but as far as I > understand, this *should* work with the hosts appearing only in > /etc/dnsmasq.conf. Or have I overlooked something ? Any suggestions > ?>From what this *looks like* after experimenting, Dnsmasq isn't 100 %able to read hostnames from dnsmasq.conf, and if I want complete local resolution, I have to put each hostname - in long and short form - in the servers' /etc/hosts file. In my case: [root at nestor:~] # cat /etc/hosts # /etc/hosts 127.0.0.1 localhost.localdomain localhost 192.168.2.1 nestor.microlinux.lan nestor 192.168.2.2 alphamule.microlinux.lan alphamule 192.168.2.3 bernadette.microlinux.lan bernadette 192.168.2.4 raymonde.microlinux.lan raymonde 192.168.2.5 amandine.microlinux.lan amandine 192.168.2.6 buzz.microlinux.lan buzz 192.168.2.7 balthazar.microlinux.lan balthazar 192.168.2.10 centosbox.microlinux.lan centosbox 192.168.2.11 susebox.microlinux.lan susebox 192.168.2.252 hp-officejet.microlinux.lan hp-officejet 192.168.2.253 nas.microlinux.lan nas 192.168.2.254 wifi.microlinux.lan wifi In my case, this works perfectly, and I can resolve local hostnames on the server and on each client. So as far as I understand, the price to pay is only a small redundancy between /etc/dnsmasq.conf and /etc/hosts. Cheers, Niki -- Microlinux - Solutions informatiques durables 7, place de l'?glise - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info at microlinux.fr T?l. : 04 66 63 10 32
Leon Fauster
2019-Jan-03 14:05 UTC
[CentOS] Erratic local hostname resolution with Dnsmasq
Am 02.01.2019 um 16:09 schrieb Nicolas Kovacs <info at microlinux.fr>:> > My local server is running CentOS 7. The machine has two NICs and is > acting as a gateway. For DHCP and DNS, I'm using Dnsmasq. I have a > strange little problem with local hostname resolution. Before going into > more details, here's my configuration. > > [root at nestor:~] # ifconfig > enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 > inet 192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255 > ether 2c:27:d7:15:54:a1 txqueuelen 1000 (Ethernet) > RX packets 17122 bytes 17596130 (16.7 MiB) > RX errors 0 dropped 0 overruns 0 frame 0 > TX packets 13426 bytes 2144915 (2.0 MiB) > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 > device interrupt 18 memory 0xfe8e0000-fe900000 > > enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 > inet 192.168.2.1 netmask 255.255.255.0 broadcast 192.168.2.255 > ether 00:22:64:8a:4c:c2 txqueuelen 1000 (Ethernet) > RX packets 6597320 bytes 9692134059 (9.0 GiB) > RX errors 0 dropped 0 overruns 0 frame 0 > TX packets 534283 bytes 57365155 (54.7 MiB) > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 > device interrupt 16 memory 0xfe9e0000-fea00000 > > [root at nestor:~] # cat /etc/hostname > nestor > > [root at nestor:~] # cat /etc/hosts > # /etc/hosts > 127.0.0.1 localhost.localdomain localhost > 192.168.2.1 nestor.microlinux.lan nestor > 192.168.2.252 hp-officejet.microlinux.lan hp-officejet > 192.168.2.253 nas.microlinux.lan nas > 192.168.2.254 wifi.microlinux.lan wifi > > [root at nestor:~] # cat /etc/resolv.conf > # /etc/resolv.conf > nameserver 127.0.0.1 > > [root at nestor:~] # cat /etc/dnsmasq.conf > # /etc/dnsmasq.conf > domain-needed > bogus-priv > interface=enp3s0 > dhcp-range=192.168.2.100,192.168.2.200,24h > local=/microlinux.lan/ > domain=microlinux.lan > expand-hosts > # Cloudflare > server=1.1.1.1 > server=1.0.0.1 > # Google > #server=8.8.8.8 > #server=8.8.4.4 > no-resolv > # Google > dhcp-host=D4:85:64:B2:B2:1B,alphamule,192.168.2.2 > dhcp-host=00:1E:C9:43:A7:BF,bernadette,192.168.2.3 > dhcp-host=00:1D:09:15:4A:D8,raymonde,192.168.2.4 > dhcp-host=00:1E:C9:42:84:7B,amandine,192.168.2.5 > dhcp-host=B8:CA:3A:D6:5A:43,1C:3E:84:32:7E:87,buzz,192.168.2.6 > dhcp-host=90:E6:BA:CF:04:8F,64:70:02:9A:AC:93,balthazar,192.168.2.7 > dhcp-host=08:00:27:00:00:01,centosbox,192.168.2.10 > dhcp-host=08:00:27:00:00:02,susebox,192.168.2.11 > dhcp-host=10:62:E5:D4:95:60,hp-officejet,192.168.2.252 > dhcp-host=00:11:32:26:63:A5,nas,192.168.2.253 > > Now here's the problem. Some of the hostname are correctly resolved, > while others are not. > ...DHCP names are registered in DNS when the clients are "online" ... -- LF