[Dnsmasq-discuss] DCHP server assign from the beginning IP addresses over and over. (no icmp's)

[Simon Kelley]

On 13/09/13 21:32, Ivan Pantovic wrote:
>
> Hi, i can't find anyone with a similar problem yet i have experienced
> quite unusual behavior of dnsmasq.
>
> In simple words it reassigns the same IP to different MAC addresses even
> if it has them in the lease file and issues no icmp/ping requests to the
> already assigned ips.
>
> I can see that no matter how many virtual machines i bring up, it always
> gives them one ip and can't record any icmp traffic during that time.
>
> (tcpdump -ni eth0 icmp gives no icmp from or to the dnsmasq host)
>
> What happens is this:
>
>> dnsmasq-dhcp: 2515134025 available DHCP range: 192.168.99.111 --
>> 192.168.99.130
>> dnsmasq-dhcp: 2515134025 DHCPREQUEST(eth1) 192.168.99.111
>> aa:8e:d8:91:48:75
>> dnsmasq-dhcp: 2515134025 tags: test, known, eth1
>> dnsmasq-dhcp: 2515134025 DHCPACK(eth1) 192.168.99.111
>> aa:8e:d8:91:48:75 vm-xxxx1-test111
>> dnsmasq-dhcp: 2515134025 requested options: 1:netmask, 28:broadcast,
>> 2:time-offset, 121:classless-static-route,
>> dnsmasq-dhcp: 2515134025 requested options: 15:domain-name,
>> 6:dns-server, 12:hostname,
>> dnsmasq-dhcp: 2515134025 requested options: 40:nis-domain,
>> 41:nis-server, 42:ntp-server,
>> dnsmasq-dhcp: 2515134025 requested options: 26:mtu, 119:domain-search,
>> 3:router
>> dnsmasq-dhcp: 2515134025 next server: 192.168.99.254
>> dnsmasq-dhcp: 2515134025 sent size:  1 option: 53 message-type  5
>> dnsmasq-dhcp: 2515134025 sent size:  4 option: 54 server-identifier
>> 192.168.99.254
>> dnsmasq-dhcp: 2515134025 sent size:  4 option: 51 lease-time  15m
>> dnsmasq-dhcp: 2515134025 sent size:  4 option: 58 T1  7m30s
>> dnsmasq-dhcp: 2515134025 sent size:  4 option: 59 T2  13m4s
>> dnsmasq-dhcp: 2515134025 sent size:  4 option:  1 netmask  255.255.255.0
>> dnsmasq-dhcp: 2515134025 sent size:  4 option: 28 broadcast
>> 192.168.99.255
>> dnsmasq-dhcp: 2515134025 sent size:  4 option:  3 router  192.168.99.254
>> dnsmasq-dhcp: 2515134025 sent size:  4 option:  6 dns-server
>> 192.168.99.254
>> dnsmasq-dhcp: 2515134025 sent size:  6 option: 15 domain-name  xxxx.com
>> dnsmasq-dhcp: 2515134025 sent size: 15 option: 12 hostname
>> vm-xxxx1-test111
>> dnsmasq-dhcp: 2515134025 available DHCP range: 192.168.99.111 --
>> 192.168.99.130
>> dnsmasq-dhcp: 2515134025 DHCPDECLINE(eth1) 192.168.99.111
>> aa:8e:d8:91:48:75
>> dnsmasq-dhcp: 2189493037 available DHCP range: 192.168.99.111 --
>> 192.168.99.130
>> dnsmasq-dhcp: 2189493037 DHCPREQUEST(eth1) 192.168.99.111
>> 9e:74:dc:32:5d:66
>> dnsmasq-dhcp: 2189493037 tags: test, known, eth1
>> dnsmasq-dhcp: 2189493037 DHCPACK(eth1) 192.168.99.111
>> 9e:74:dc:32:5d:66 vm-xxxx1-test111
>
> this are the options currently used:
>
>> [root at vm-xxxx1-gw1 ~]# fgrep -v '#' /etc/dnsmasq.conf | sed -e '/^$/d'
>> except-interface=eth0
>> dhcp-sequential-ip
>> dhcp-ignore-names
>> domain=xxxx.com
>> dhcp-host=id:tester,set:test
>> dhcp-range=tag:test,192.168.99.111,192.168.99.130,15m
>> dhcp-leasefile=/var/lib/misc/dnsmasq.leases
>> dhcp-authoritative
>> log-dhcp
>
>> [root at vm-xxxx-gw1 ~]# uname -a
>> Linux vm-xxxx-gw1 3.10.10-1-ARCH #1 SMP PREEMPT Fri Aug 30 11:30:06
>> CEST 2013 x86_64 GNU/Linux
>
> the iptables are clear and the VM's and dnsmasq are on the same l2 part
> of the network.
>
> i can't clearly see how the decision is made in source to ping or not to
> ping the address but obviously something is not working properly.
>
> and yes my /etc/hosts file holds the names for the VM's. For the first
> VM it works great but then since the discovery of ip's in use is not
> working properly (and it might be something else since it also ignores
> the own leases file) it continue to assign the same first or second
> address (i didn't get further then that).
>
>
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> Dnsmasq-discuss at lists.thekelleys.org.uk
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>


One possibility: are the VMs all cloned from the same image which has 
the same DHCP client-id baked in? Dnsmasq will use the client-id in 
preference to the MAC address to identify clients.

The client-id is stored as the last field on each line of the leases file.

If that's not the problem, does it work if  you remove the 
dhcp-sequential-ip configuration. That's not often used, so a bug could 
be lurking there.


Cheers,

Simon.