[Dnsmasq-discuss] No new lease for Option 82 requests until old one times out

Kincl, Jason C. kincljc at ornl.gov
Wed Sep 17 16:33:29 BST 2014


Hi,

I completely agree with Joachim and have also run into this issue while
using Option-82. Also, since each lease is tied to a client identifier, I
have seen issues where the PXE client will give a different identifier
from the OS and DNSMasq will refuse to hand out the IP thinking that the
pool is exhausted. This specific problem has been discussed before[1] on
the list. But I think if we could get away from using dhcp-range with
Option-82 and use dhcp-host with tag:tag syntax then we could solve these
problems. I also asked about dhcp-host with tags on this list[2] a few
weeks ago but Joachim¹s post is significantly more elegant and descriptive.

Thanks!


[1] 
http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2014q1/008067.html

[2] 
http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2014q3/008785.html


-- 
Jason Kincl



On 9/17/14, 7:00 AM, "dnsmasq-discuss-request at lists.thekelleys.org.uk"
<dnsmasq-discuss-request at lists.thekelleys.org.uk> wrote:

>Date: Wed, 17 Sep 2014 10:49:16 +0200
>From: Joachim Nilsson <troglobit at gmail.com>
>To: dnsmasq discuss <dnsmasq-discuss at lists.thekelleys.org.uk>
>Subject: [Dnsmasq-discuss] No new lease for Option 82 requests until
>	old one	times out
>Message-ID: <54194B0C.7010802 at gmail.com>
>Content-Type: text/plain; charset=utf-8; format=flowed
>
>Hi Simon,
>
>I've found a little problem with how Option 82 circuit-id/remote-id
>works. Everything is fine in the below setup until I replace the client
>with a replacement unit that has a different MAC.
>
>     [client]---LAN1---[dhcrelay]---LAN2---[dnsmasq]
>
>dhcp-range=subnet0,tag:!static,192.168.2.100,192.168.2.199,255.255.255.0,8
>64000
>
>     dhcp-circuitid=set:cid0,"Eth6"
>     tag-if=set:static,set:tag0,tag:cid0
>dhcp-range=tag:tag0,192.168.2.99,192.168.2.99,255.255.255.0,864000
>
>When 'client' is replaced the request from the new client reaches
>dnsmasq, which responds with "no address available".  I figured this is
>because the "pool" for the static IP only has one entry, bound to the
>old client's MAC.  Indeed, it is not until the lease for the old client
>times out that the new client receives an offer. I guess this behavior
>is by design ...
>
>I was thinking that adding 'tag:tag0' to the --dhcp-host setting would
>have been perfect for Option 82, since they're basically static leases
>anyway -- the same port on a given switch should always receive the same
>IP ... so adding tag support, in addition to the already existing mac
>and client-id, seemed at least to me useful.
>
>What do you think?
>
>Regards
>  /Joachim
>
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