7:06 a.m.
Who or what decides the length of a dhcp lease?
I notice that the computers accessing my desktop dhcpd server
have widely different lease times.
The laptop I'm currently using, for example,
has a lease time of about half-an-hour
according to /var/lib/dhclient/dhclient-eth1.leases:
-----------------------------
renew 2 2008/1/29 13:08:12;
rebind 2 2008/1/29 13:34:10;
expire 2 2008/1/29 13:41:40;
-----------------------------
But the server sets the time much longer,
according to /etc/dhcpd.conf on my desktop:
-----------------------------
default-lease-time 21600;
max-lease-time 43200;
-----------------------------
Can the client change the lease times?
Or is it entirely up to the server?
[My grand-daughter's Wii seems to have an even shorter lease time,
at least it exchanges DHCPREQUEST/DHCPACK with the server every 2 minutes.]
Is there an online document that will instruct me on this?
--
Timothy Murphy
e-mail (<80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland
7:51 a.m.
Around 01:06pm on Tuesday, January 29, 2008 (UK time), Timothy Murphy scrawled:
[My grand-daughter's Wii seems to have an even shorter lease
time,
at least it exchanges DHCPREQUEST/DHCPACK with the server every 2 minutes.]
Funnily enough I have been thinking exactly the same thing, having got
the kids a wii for xmas. Not much help except to confirm what you say
is true (though mine seems to be about every 6 - 8 minutes.
Steve
--
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8:03 a.m.
On Tue, 2008-01-29 at 13:06 +0000, Timothy Murphy wrote:
Who or what decides the length of a dhcp lease?
The server. It doles out the lease, the client just *asks* for what it
wants, and has to make do with what it gets.
You have configuration options on the server for the maximum, and
defaults. The client can ask for what it wants, but the server will
ultimately decide. Before the lease expires, the client will ask for it
to be renewed. Going from memory, it asks at the half-way point.
On some clients you can configure the values it asks for, others not,
and the defaults for different clients are different.
Configure your server as you want leases to be handled (the maximum and
minimum possible lease times, and your preferred defaults). Configure
your clients, if you want something particular for those clients, or
leave them be.
My grand-daughter's Wii seems to have an even shorter lease
time,
at least it exchanges DHCPREQUEST/DHCPACK with the server every 2
minutes
Reminds me of the haggling scene in The Life of Brian... 2 minutes for
this lease? You must be mad...
But I can see why they'd set short ones for games, people expect games
to just plug in and start working. Having to put up with long delays
while changes take place would be untenable, particularly with
multi-machine network gaming. But if you had a network where the only
thing was changing was that one Wii, and you didn't want it doing it
that rapidly, you'd set the servers minimum lease time to be longer, and
the Wii would have to put up with a longer lease time.
--
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important to the thread.)
Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.
5:04 p.m.
Tim wrote:
Reminds me of the haggling scene in The Life of Brian... 2 minutes for
this lease? You must be mad...
But I can see why they'd set short ones for games, people expect games
to just plug in and start working. Having to put up with long delays
while changes take place would be untenable, particularly with
multi-machine network gaming. But if you had a network where the only
thing was changing was that one Wii, and you didn't want it doing it
that rapidly, you'd set the servers minimum lease time to be longer, and
the Wii would have to put up with a longer lease time.
Leases should not be renewed too often; any renewal process takes more
time than not renewing.
In an office where laptops may come and go (but always the same ones) I
figure one day is fine, they'll probably not renew during a working day,
but are required to next day.
In the ordinary course of events, everyone gets the same IP address each
time.
For PXE I might give a short lease, it's only going to run for a few
seconds, and Anaconda maybe an hour or so.
I do give different answers, depending on who's asking.
--
Cheers
John
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7:59 a.m.
On Wed, 2008-01-30 at 08:04 +0900, John Summerfield wrote:
Leases should not be renewed too often; any renewal process takes
more
time than not renewing.
And if DNS updating's involved, even more work.
I tend to set mine for several days. That'll nearly always mean the
same box gets the same IP.
I do give different answers, depending on who's asking.
I should write a witty comment, now... :-\
--
Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.
8:55 a.m.
John Summerfield wrote:
For PXE I might give a short lease, it's only going to run for a
few
seconds, and Anaconda maybe an hour or so.
I do give different answers, depending on who's asking.
How do you change the lease-time for different machines?
I'm puzzled by the different lease-times I get on different laptops,
connecting to the same desktop.
The laptop I'm on now gets about 30 minutes:
--------------------------------
Jan 30 13:53:18 mary dhclient: DHCPREQUEST on eth1 to 192.168.2.1 port 67
Jan 30 13:53:18 mary dhclient: DHCPACK from 192.168.2.1
Jan 30 13:53:18 mary dhclient: bound to 192.168.2.19 -- renewal in 1687
seconds.
--------------------------------
Another laptop gets about 3 hours:
--------------------------------
Jan 7 14:36:11 carrie dhclient: DHCPREQUEST on eth0 to 192.168.2.1 port 67
Jan 7 14:36:11 carrie dhclient: DHCPACK from 192.168.2.1
Jan 7 14:36:11 carrie dhclient: bound to 192.168.2.4 -- renewal in 9591
seconds.
--------------------------------
Who or what exactly decides on these lease-times?
The entries for the 2 laptops in /etc/dhcpd.conf on the desktop
are identical:
--------------------------------
host carrie {
hardware ethernet 00:15:00:16:2A:EA;
fixed-address 192.168.2.4;
}
host mary {
hardware ethernet 00:02:2D:21:03:B1;
fixed-address 192.168.2.19;
}
--------------------------------
The only difference I see is that mary is running Fedora-8
while carrie is running Fedora-7.
Any elucidation gratefully received.
--
Timothy Murphy
e-mail (<80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland
9:33 a.m.
On Wed, 2008-01-30 at 14:55 +0000, Timothy Murphy wrote:
The only difference I see is that mary is running Fedora-8
while carrie is running Fedora-7.
That's probably just down to different defaults in the clients. The
server offers something, the clients can ask for something else. If the
server doesn't object, that's what they get.
To work it out, try putting some lease time parameters into
their /etc/dhclient-*.conf files. My laptop has two,
"dhclient-eth0.conf" & "dhclient-wlan0.conf", both of which are
almost
empty. But I can add things to them.
Alternatively, you could try squeezing things in from the server, and
see what happens. e.g. Set your min, max, & default, lease times to 2
hours.
--
(This computer runs FC7, my others run FC4, FC5 & FC6, in case that's
important to the thread.)
Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.
8:04 a.m.
Timothy Murphy wrote:
Who or what decides the length of a dhcp lease?
I notice that the computers accessing my desktop dhcpd server
have widely different lease times.
The laptop I'm currently using, for example,
has a lease time of about half-an-hour
according to /var/lib/dhclient/dhclient-eth1.leases:
-----------------------------
renew 2 2008/1/29 13:08:12;
rebind 2 2008/1/29 13:34:10;
expire 2 2008/1/29 13:41:40;
-----------------------------
But the server sets the time much longer,
according to /etc/dhcpd.conf on my desktop:
-----------------------------
default-lease-time 21600;
max-lease-time 43200;
-----------------------------
Can the client change the lease times?
Or is it entirely up to the server?
[My grand-daughter's Wii seems to have an even shorter lease time,
at least it exchanges DHCPREQUEST/DHCPACK with the server every 2 minutes.]
Is there an online document that will instruct me on this?
The server sets an expiration time when it gives the IP and clients
typically start to request renewals halfway to the expiration time but
if they don't get a response, will keep using the IP up till expiration.
--
Les Mikesell
lesmikesell(a)gmail.com
5991
days inactive
5992
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7 comments
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Timothy Murphy