[Dnsmasq-discuss] Disappearing hosts from local DNS resolution

richardvoigt at gmail.com richardvoigt at gmail.com
Wed Oct 8 05:50:13 BST 2008


What is the IP address of your dnsmasq?  Do you have any other nodes
running udp servers on the bootp ports?  (netstat -a to check)

It looks as if that log was from lease expiration, because dnsmasq
didn't find a matching lease and then NACKed.  Can you verify that
there are no log entries (renew attempt) being made on the client at
the half-way time?

On Tue, Oct 7, 2008 at 3:58 PM, Eric Thibodeau <kyron at neuralbs.com> wrote:
> richardvoigt at gmail.com wrote:
>
> Nope, seems dhcpcd is not requesting a renew of the lease at 1/2 time as
> it should (IIRC). http://wiki.neuralbs.com/~kyron/DHCP_reqs_tb17 contains
> a grep of the DHCP activity from the disappearing nodes int
> /var/log/messages.
>
>
> Can you get a client-side log, or even better packet capture?
> DISCOVER and RENEW requests may look different enough to match
> firewall rules differently.  For example, DISCOVER sent to broadcast
> address and RENEW sent unicast.
>
>
> Oct  7 11:50:52 thinkbig16 dhcpcd[29651]: eth0: sending signal 14 to pid
> 21865
> Oct  7 11:50:52 thinkbig16 dhcpcd[21865]: eth0: received SIGALRM, renewing
> lease
> Oct  7 11:50:52 thinkbig16 dhcpcd[21865]: eth0: renewing lease of 10.0.1.136
> Oct  7 11:50:52 thinkbig16 dhcpcd[21865]: eth0: NAK: lease not found from
> 10.0.1.129
> Oct  7 11:50:52 thinkbig16 dhcpcd[29652]: eth0:
> /lib/dhcpcd/dhcpcd-run-hooks: Network is unreachable
> Oct  7 11:50:53 thinkbig16 dhcpcd[21865]: eth0: broadcasting for a lease
> Oct  7 11:50:53 thinkbig16 dhcpcd[21865]: eth0: offered 10.0.1.136 from
> 10.0.1.136 `boothost'
> Oct  7 11:50:53 thinkbig16 dhcpcd[21865]: eth0: ignoring offer of 10.0.1.136
> from 10.0.1.136 `boothost'
> Oct  7 11:50:53 thinkbig16 dhcpcd[21865]: eth0: acknowledged 10.0.1.136 from
> 10.0.1.136 `boothost'
> Oct  7 11:50:53 thinkbig16 dhcpcd[21865]: eth0: checking 10.0.1.136 is
> available on attached networks
> Oct  7 11:50:59 thinkbig16 dhcpcd[21865]: eth0: leased 10.0.1.136 for 43200
> seconds
>
> So the lease time is explicitly received as being 12h (which is correct) but
> the " eth0: offered 10.0.1.136 from 10.0.1.136 `boothost' " has got me
> frowning... (note that `boothost' is defined in the config pasted below)
>
> The tcpdump file is available at:
> http://wiki.neuralbs.com/~kyron/dhcpout_tb16 sorry for the net chatter but
> you get it all there ;)
>
> What does your network topology look like? Are you using DHCP relays
> and/or a not-fully-routed IP network? It's possiblr for hosts to be able
> to get a network, but not renew it under some circumstances.
>
>
> Ok at the risk of being flamed about network topology, I have a hacked up
> setup but it shouldn't impact DHCP IMHO (I'm emulating NIC bonding through
> IP masking).
>
> Here is the setup:
>
> http://wiki.neuralbs.com/~kyron/HyperTransport/ClusterNetDiagram.png
>
> Here is the config file (sourced by dnsmasq.conf)
> eric at headless ~/1_Files/1_ETS/1_Maitrise/Code/pvq $ cat
> /etc/dnsmasq.AthlonXP_All.conf
> # On force le broadcast à 10.0.1.255
> dhcp-option=28,10.0.1.255
>
> #The group name,address range and lease time:
> dhcp-range=AthlonXP_1,10.0.1.10,10.0.1.126,255.255.255.0,12h
> # The GROUP_NAME's,option 3:default Gateway (if you really need this, nodes
> shouldn't require routed access):
> dhcp-option=AthlonXP,3,10.0.1.1
> # The GROUP_NAME's, option 42:time server address:
> dhcp-option=AthlonXP_1,42,10.0.1.1
> # This is required for PXE booting
> dhcp-boot=net:AthlonXP_1,/pxelinux.0,boothost,10.0.1.1
> # As can be seen in the dnsmasq.conf, this option is not guaranteed to work
> (DN search order)
> dhcp-option=AthlonXP_1,119,cluster.local
> # Domain DNS name
> dhcp-option=15,cluster.local
> # NIS domain
> dhcp-option=40,cluster.local
>
> # Now for the host listing, format is:
> # dhcp-host=MACADDRESS,net:GROUP_NAME,NODE_NAME,IP_ADDRESS
> dhcp-host=00:01:03:df:ca:44,net:AthlonXP_1,thinkbig1,10.0.1.11
> dhcp-host=00:01:03:DF:C6:38,net:AthlonXP_1,thinkbig2,10.0.1.12
> dhcp-host=00:01:03:DF:D3:30,net:AthlonXP_1,thinkbig3,10.0.1.13
> dhcp-host=00:01:03:DF:D3:08,net:AthlonXP_1,thinkbig4,10.0.1.14
> dhcp-host=00:01:03:DF:D3:01,net:AthlonXP_1,thinkbig5,10.0.1.15
> dhcp-host=00:01:03:DF:CA:3B,net:AthlonXP_1,thinkbig6,10.0.1.16
> dhcp-host=00:04:75:C2:21:14,net:AthlonXP_1,thinkbig7,10.0.1.17
> dhcp-host=00:01:03:DF:CA:46,net:AthlonXP_1,thinkbig8,10.0.1.18
> dhcp-host=00:01:03:de:5f:2e,net:AthlonXP_1,thinkbig9,10.0.1.19
>
> #
> # The group name,address range and lease time:
> dhcp-range=AthlonXP_2,10.0.1.130,10.0.1.254,255.255.255.0,12h
> # The GROUP_NAME's,option 3:default Gateway (if you really need this, nodes
> shouldn't require routed access):
> dhcp-option=AthlonXP_2,3,10.0.1.129
> # The GROUP_NAME's, option 42:time server address:
> dhcp-option=AthlonXP_2,42,10.0.1.129
> # This is required for PXE booting
> dhcp-boot=net:AthlonXP_2,/pxelinux.0,boothost,10.0.1.129
> # As can be seen in the dnsmasq.conf, this option is not guaranteed to work
> (DN search order)
> #dhcp-option=AthlonXP_2,119,cluster.local
> # Now for the host listing, format is:
> # dhcp-host=MACADDRESS,net:GROUP_NAME,NODE_NAME,IP_ADDRESS
>
> dhcp-host=00:01:03:DE:B5:C3,net:AthlonXP_1,thinkbig10,10.0.1.130
> dhcp-host=00:01:03:DE:B6:AE,net:AthlonXP_1,thinkbig11,10.0.1.131
> dhcp-host=00:04:75:AA:36:5B,net:AthlonXP_1,thinkbig12,10.0.1.132
> dhcp-host=00:01:03:DF:CA:42,net:AthlonXP_2,thinkbig13,10.0.1.133
> dhcp-host=00:01:03:DE:B5:C2,net:AthlonXP_2,thinkbig14,10.0.1.134
> dhcp-host=00:01:03:24:E9:3B,net:AthlonXP_2,thinkbig15,10.0.1.135
> dhcp-host=00:04:75:EC:33:47,net:AthlonXP_2,thinkbig16,10.0.1.136
> dhcp-host=00:04:75:EC:4E:F2,net:AthlonXP_2,thinkbig17,10.0.1.137
> #dhcp-host=00:04:75:EC:4E:CF,net:AthlonXP_2,thinkbig18,10.0.1.138
>
>



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