[Dnsmasq-discuss] Sequential IP doesn't look for unused IPs

Albert ARIBAUD albert.aribaud at free.fr
Sat Dec 24 08:32:54 GMT 2016


Hi Alec,

Le Fri, 23 Dec 2016 20:04:55 -0500
Alec Robertson <alecrobertson13 at gmail.com> a écrit:

> When using sequential IP, the IP allocation should start from the
> lowest available IP address.
> 
> However, if the lease time is quite short for the clients, the
> clients can renew their IP addresses and be given IP addresses that
> don’t use the entire range available, meaning that you could have a
> range that starts at say 1 but this IP address is never used again
> because the sequential IP system does not look for IPs that aren’t
> “filled”. Instead, it simply goes for the lowest available IP that is
> available after the last one that was allocated.
> 
> I am sorry for my very poor description but I tried the best I could
> to explain this problem.

There might be a misunderstanding about "sequential" here.

You seem to think that dhcp-sequential-ip will cause dnsmasq to
react to every request by searching upward from the range start for the
first available IP.

I suspect what it does for every request is search for the first
available IP from the last point it had reached so far; beginning at
the range start is just what happens for the very first request
received.

IOW, you think it always allocates the lowest currently free IP whereas
I suspect it will actually allocate the lowest free IP above the last
one allocated.

My suspicion comes from the fact that the sequential behavior is
probably named after its visible effect, i.e. going over the full range
in sequence even if older IP were freed in between. 

Amicalement,
-- 
Albert.



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