[Dnsmasq-discuss] No DHCPOffer back but DHCPDiscover is being received by machine

Geert Stappers stappers at stappers.nl
Tue Apr 14 20:04:25 BST 2020


On Tue, Apr 14, 2020 at 06:51:25PM +0100, Josh H wrote:
> Hi there,
> 
> I'm receiving no DHCPOffer back from my DHCPDiscover. However, I can
> tcpdump the machine running dnsmasq and it is receiving the DHCPOffer
> packets.
 
Acknowledge


> Here's my very very simple dnsmasq.conf
> # To disable dnsmasq's DNS server functionality.
> port=0
> 
> # To enable dnsmasq's DHCP server functionality.
> dhcp-range=192.168.1.3,192.168.1.8,255.255.255.240,12h
> 
> # Set gateway as Router. Following two lines are identical.
> #dhcp-option=option:router,192.168.0.1
> dhcp-option=3,192.168.0.1
> 
> # Set DNS server as Router.
> dhcp-option=6,192.168.0.1
> 
> # Logging.
> log-facility=/var/log/dnsmasq.log   # logfile path.
> log-async
> log-queries # log queries.
> log-dhcp    # log dhcp related messages.

Acknowledge on `log DHCP`


> 
> Here's the contents of /var/log/dnsmasq.log after running dhclient on a
> machine connected to the subnet:
> Apr 14 18:36:57 dnsmasq[1702]: started, version 2.80 DNS disabled
> Apr 14 18:36:57 dnsmasq[1702]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify dumpfile
> Apr 14 18:36:57 dnsmasq-dhcp[1702]: DHCP, IP range 192.168.1.3 -- 192.168.1.8, lease time 12h
 
Missing DHCP related entries ...


> I can see the service running with netstat -anp4:
> Active Internet connections (servers and established)
> Proto Recv-Q Send-Q Local Address    Foreign Address   State PID/Program name
> udp        0      0 0.0.0.0:67       0.0.0.0:*         1702/dnsmasq
> udp        0      0 0.0.0.0:1701     0.0.0.0:*         1607/xl2tpd
> 
> There are no firewalls setup anywhere on my network for the moment. I have
> been able to get isc-dhcp-server to successfully allocate DHCP requests
> just fine however, so I don't think it's anything broken with DHCP in
> general. I'm running Linux kernel 5.6.2 and using dnsmasq from Debian
> Bullseye.
> 
> Hopefully someone can work out my issue!

You already have met the best someone   ;-)

Tell more about the set up  in use.

My hope is that it provides some clue why `tcpdump` can see DHCP network
traffic that `dnsmasq` should seen also.


> Thank you very much!

Thank you for reporting in an interresting problem.



Regards
Geert Stappers
-- 
Silence is hard to parse



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