[Dnsmasq-discuss] Simple dnsmasq configuration as DHCP server issue

[Simon Kelley]

On 16/11/12 15:00, Tomas Hozza wrote:
> Hello.
> 
> I'm having some problems with configuring dnsmasq as a DHCP server.
> 
> Interface configuration with DHCP off and static IP address:
> [root at localhost ~]# ifconfig
> eth0: flags=4163MULTICAST>  mtu 1500
>         inet 192.168.222.2  netmask 255.255.255.0  broadcast 192.168.222.255
>         inet6 fe80::5054:ff:fe37:d318  prefixlen 64  scopeid 0x20
>         ether 52:54:00:37:d3:18  txqueuelen 1000  (Ethernet)
>         RX packets 626  bytes 158950 (155.2 KiB)
>         RX errors 0  dropped 0  overruns 0  frame 0
>         TX packets 1478  bytes 285104 (278.4 KiB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
>         device interrupt 11  base 0xe000
> 
> dnsmasq command:
> [root at localhost ~]# /sbin/dnsmasq -d --strict-order --bind-dynamic --domain-needed --conf-file= --listen-address 192.168.222.2 --dhcp-range 192.168.222.10,192.168.222.254 --dhcp-leasefile=net.leases --dhcp-lease-max=243 --dhcp-no-override
> dnsmasq: started, version 2.63rc6 cachesize 150
> dnsmasq: compile time options: IPv6 GNU-getopt DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack
> dnsmasq-dhcp: DHCP, IP range 192.168.222.10 -- 192.168.222.254, lease time 1h
> dnsmasq: reading /etc/resolv.conf
> dnsmasq: using nameserver 192.168.122.1#53
> dnsmasq: read /etc/hosts - 2 addresses
> 
> [root at localhost ~]# netstat -anp | grep dnsmasq
> tcp        0      0 192.168.222.2:53        0.0.0.0:*               LISTEN      4919/dnsmasq        
> udp        0      0 192.168.222.2:53        0.0.0.0:*                           4919/dnsmasq        
> udp        0      0 0.0.0.0:67              0.0.0.0:*                           4919/dnsmasq
> 
> [root at localhost ~]# tcpdump -vv -i eth0
> tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
> 14:44:36.731716 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
>     0.0.0.0.bootpc > 192.168.222.2.bootps: [udp sum ok] BOOTP/DHCP, Request from 52:54:00:c6:c4:0d (oui Unknown), length 300, xid 0x2425bc3e, secs 57, Flags [none] (0x0000)
>           Client-Ethernet-Address 52:54:00:c6:c4:0d (oui Unknown)
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Discover
>             Parameter-Request Option 55, length 13:
>               Subnet-Mask, BR, Time-Zone, Classless-Static-Route
>               Domain-Name, Domain-Name-Server, Hostname, YD
>               YS, NTP, MTU, Option 119
>               Default-Gateway
> 
> As you can see, there are incoming DHCP Requests,
> but dnsmasq doesn't answer them and the client is
> unable to get IP address.
> 
> There is another colleague having the same problem,
> and he verified, that when he replace dnsmasq with
> dhcpd the client got an IP address. Therefore it seems
> like dnsmasq issue.
> 
> Can anyone please help us with this issue?
> 

The first thing I worry about whenever anyone tells me that dnsmasq
ignores DHCP requests but ISC dhcpd works, is firewall/iptables rules.
You have to ensure that source address 0.0.0.0 and/or destination
address 255.255.255.255 are not intercepted. This will not affect dhcpd,
but it does affect dnsmasq.


You configuration looks fine on a casual inspection.



Cheers,

Simon.