Re: Does DNSMasq (or other DNS/DHCP Servers) Cache Old Addresses?
On Tue, Mar 03, 2009 at 03:56:04AM -0500, Hal Vaughan wrote:
> I'm adding a new system to my LAN. The DNS is running DNSMasq and is on
> Etch. The new system is running Lenny. I edited the /etc/network/
> interfaces file to include the following (other than loopback, the only
> interface in the file):
>
> auto eth0
> iface eth0 inet static
> address 172.16.7.111
> netmask 255.255.0.0
> gateway 172.16.7.1
>
> Originally, when Debian set up the system, it used DHCP instead of a
> static IP. This IP address (172.16.7.111) is defined on the DNS server
> in /etc/hosts (which DNSMasq uses for config). When Debian-Lenny set
> this up under DHCP, it was assigned the address 172.16.7.131. I edited
> the interfaces file to include the above. If I did
> "/etc/init.d/networking restart," then it would again get the ...131
> address. If I did "ifup eth0" (after doing ifdown first), then it'd get
> the 111 address it should have, but in at least one case, a few minutes
> later I checked and it was back to 131.
>
> I finally shut down the new system and rebooted the DNS server -- after
> having shut off networking on the new system and restarting DNSMasq on
> the DNS. Then I brought up the DNS server, and after that, brought up
> the new system. Now it's working and it finally let me define eth0:0 as
> well (which it kept choking on before).
>
> So why did it keep getting forced to use the 172.16.7.131 address
> instead of the one ending in 111? Did DNSMasq cache the MAC address or
> did the new workstation cache the info and reuse it automatically? What
> was it that the reboot would have restarted that would allow this system
> to finally get the specified address after the reboot?
The log of dnsmasq is at /var/log/daemon.log .
When your computer asks for an address, does it:
* Just use DHCPDISCOVER ?
* Uses DHCPDISCOVER but with a preferred IP address?
* Uses DHCPREQUEST directly?
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