[Dnsmasq-discuss] Disappearing hosts from local DNS resolution

[Simon Kelley]

Eric Thibodeau wrote:
> Hello,
> 
>    I am using dnsmasq as a core component of my cluster. I'm having a 
> weird problem where the nodes are disappearing (can't use hostnames 
> anymore). So I am forced to connect to them using the IP addr. and 
> forcing dhcpcd to request an IP for the hosts to reappear in dnsmasq. 
> The logs show the following on the disappeared hosts:
> 
> Oct  1 15:29:41 headless dnsmasq[7726]: DHCPREQUEST(eth1) 10.0.1.11 
> 00:01:03:df:ca:44
> Oct  1 15:29:41 headless dnsmasq[7726]: DHCPNAK(eth1) 10.0.1.11 
> 00:01:03:df:ca:44 lease not found
> ...
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPDISCOVER(eth1) 
> 00:01:03:df:ca:44
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPOFFER(eth1) 10.0.1.11 
> 00:01:03:df:ca:44
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPDISCOVER(eth2) 
> 00:01:03:df:ca:44
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPOFFER(eth2) 10.0.1.11 
> 00:01:03:df:ca:44
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPREQUEST(eth1) 10.0.1.11 
> 00:01:03:df:ca:44
> Oct  1 15:29:42 headless dnsmasq[7726]: DHCPACK(eth1) 10.0.1.11 
> 00:01:03:df:ca:44 thinkbig1
> 
>   Here are two significant lines from my config file:
> 
> dhcp-range=AthlonXP_1,10.0.1.10,10.0.1.126,255.255.255.0,12h
> 
> dhcp-host=00:01:03:df:ca:44,net:AthlonXP_1,thinkbig1,10.0.1.11
> 
> As you can note, I am defining a range with a lease time of 12h but none 
> for the statically defined hosts. Could this be the reason the nodes 
> disappear (lease time not sent to nodes if it's not defined in the 
> static definition)?

Not a problem, if the lease time is not given, it defaults to the value 
for the range.
> 
> dnsmasq version is 2.45 and dhcpcd is 4.0.1-rc1
> 

The reaon the host is not in DNS is because there is no lease for it in 
dnsmasq's lease database. The dhcp-host line tells dnsmasq what address 
to offer, but it's the existence of a lease that gets reflected into the 
DNS,

Something is mangling your lease database, hence when the host tries to 
renew its lease:
 >Oct  1 15:29:41 headless dnsmasq[7726]: DHCPREQUEST(eth1) 10.0.1.11
 > 00:01:03:df:ca:44
 > Oct  1 15:29:41 headless dnsmasq[7726]: DHCPNAK(eth1) 10.0.1.11
 > 00:01:03:df:ca:44 lease not found
                     ^^^^^^^^^^^^^^^

Are you doing something odd with the leases file?

Simon.