On Fri, Nov 29, 2019 at 10:15:22AM +0200, Johan Kruger wrote: > On Thu, Nov 28, 2019 at 09:49:43PM +0200, Johan Kruger wrote: > > Hi, > > > > I have a fairly simple DHCP setup on a Raspbian box, using dnsmasq > > 2.80. The relavant options in /etc/dnsmasq.conf are (yes, my home LAN > > is 10.168.8.0/24): > > > > dhcp-range=10.168.8.10,10.168.8.200 # Also tried with 12h on the end, no > > difference > > dhcp-authoritative > > log-dhcp > > > > I'm testing by running "dnsmasq -d" in a shell, so I can see what's going > > on. > > > > When dnsmasq gets a DHCP request (I'm using "nmap --script > > broadcast-dhcp-discover" on another box to test), I see the following: > > > > dnsmasq-dhcp: 811185697 broadcast response > > dnsmasq-dhcp: 811185697 sent size: 1 option: 53 message-type 2 > > dnsmasq-dhcp: 811185697 sent size: 4 option: 54 server-identifier > > 10.168.8.254 > > dnsmasq-dhcp: 811185697 sent size: 4 option: 51 lease-time 2m > > dnsmasq-dhcp: 811185697 sent size: 4 option: 58 T1 1m > > dnsmasq-dhcp: 811185697 sent size: 4 option: 59 T2 1m45s > > dnsmasq-dhcp: 811185697 sent size: 4 option: 1 netmask 255.255.255.0 > > dnsmasq-dhcp: 811185697 sent size: 4 option: 28 broadcast 10.168.8.255 > > dnsmasq-dhcp: 811185697 sent size: 4 option: 3 router 10.168.8.254 > > dnsmasq-dhcp: 811185697 sent size: 4 option: 6 dns-server 10.168.8.254 > > dnsmasq-dhcp: 811185697 sent size: 16 option: 15 domain-name myhome > > > > Notice the lease-time, T1 and T2 responses... 2 minutes??? Default > > should be 1 hour, and I get the same 2m if I specify 12h in the > > dhcp-range line. > > > > > > I then added the following to the conf file: > > > > dhcp-option=51,12h > > dhcp-option=58,12h # DHCP Renewal (T1) Time > > dhcp-option=59,12h # DHCP Rebinding (T2) Time > > > > Then the response looked like this: > > > > dnsmasq-dhcp: 1994188113 broadcast response > > dnsmasq-dhcp: 1994188113 sent size: 1 option: 53 message-type 2 > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 54 server-identifier > > 10.168.8.254 > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 51 lease-time 2m > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 58 T1 1m > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 59 T2 1m45s > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 1 netmask 255.255.255.0 > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 28 broadcast 10.168.8.255 > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 3 router 10.168.8.254 > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 6 dns-server 10.168.8.254 > > dnsmasq-dhcp: 1994188113 sent size: 16 option: 15 domain-name myhome > > dnsmasq-dhcp: 1994188113 sent size: 4 option: 51 lease-time 12h > > > > > > Two lease-time responses, at least the correct 12h one is second so > > the client uses that, but notice that T1 and T2 are still wrong. > > > > When I started running dhcpdump to do more diagnostics (when > isc-dhcp-server stared responding with 5 minute lease times) I > discovered that the nmap command I was using to test was specifically > requesting a 1 second lease, so dnsmasq was replying with the default > minimum lease time of 2 minutes... oops. Thanks for reporting back.
Yes, networksniffers (dhcpdump and friends) are really cool tools. Infact "must have tools". Groeten Geert Stappers -- Meten is weten, als je maar weet wat je meet. _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss