plz help ......realated to leases allocation
hitesh sharma
engineerhitesh at gmail.com
Tue Feb 13 11:01:15 UTC 2007
hi ... thanks a lot ......
but i m talking @ the fixed leases , which in defined inside the
dhclient.conf file inside leases statement. so , plz tell me smthing about
that
On 2/13/07, Randy Grimshaw <rgrimsha at syr.edu> wrote:
> your message came through badly formatted and hard to read, but I
> suspect that you misunderstand the mechanics of a static lease. In a
> static lease the client will always receive the same address from the
> dhcp server when in that subnet. The client will still need to obtain
> the address from the server. If the server is absent, the mechanism
> fails. There are IP profiles in some OS that work as optional
> configurations to use when attached to different networks, which may be
> used to simplify a manual configuration in the absence of a dhcp
> server... but these should be considered unrelated to the dhcp protocol.
> <><Randy
>
>
> <><Randall Grimshaw
> Room 203 Machinery Hall
> Syracuse University
> Syracuse, NY 13244
> 315-443-5779
> rgrimsha at syr.edu
> >>> hitesh at elitecore.com 02/13/07 5:19 AM >>>
> Content-Type: Text/Plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
> =0D
> =0D
> =0D
> thanks ....................=0D
> some of my questions is unable to understand u , so now i will try
> to=
> =0D
> explain u ........=0D
> 1> actually , i want to know about the fixed leases which is declared
> in=0D
> client's .conf file , let suppose when there is no dhcp server ,
> then=0D
> client will assign the fixed leases which one is declared in leases=0D
> statement , but i want to know , that what i will have to do , that
> clien=
> t=0D
> will automatically detect the server when server comes into lan ?=0D
> =0D
> 2> in client's .conf file , when i declared fixed leases , i.e.
> inside=0D
> leases statement , then there is three fields renew , rebind , and
> expir=
> y .=0D
> so what is=0D
> significance of them .=0D
> 3 > we know that in client .conf file , after "timeout statement "
> ,=
> =0D
> client will assign the fixed leases (when there is no valid leases in=0D
> leases file ) , but i want to know , once fixed leases allocated to
> clien=
> t ,=0D
> then retry statement will execute ?=0D
> i am also copying , my chclient.conf file , plz take a look of this
> .=
> =2E..=0D
> =2E...............=0D
> =0D
> send dhcp-lease-time 60;=0D
> request subnet-mask, broadcast-address, time-offset, routers,=0D
> domain-name, domain-name-servers, host-name;=0D
> require subnet-mask, domain-name-servers, routers;=0D
> timeout 20;=0D
> retry 30; // i want to know about this statement=0D
> reboot 10;=0D
> select-timeout 5;=0D
> initial-interval 2;=0D
> script "/sbin/dhclient-script";=0D
> #media "-link0 -link1 -link2", "link0 link1";=0D
> #interface "eth0" {=0D
> # reject 192.168.0.76;=0D
> # send dhcp-lease-time 400;=0D
> # send dhcp-client-identifier 00:0C:29:B1:A6:32;=0D
> # }=0D
> =0D
> #interface "eth1" {=0D
> # send dhcp-client-identifier 00:0C:29:B1:A6:3C;=0D
> # send dhcp-lease-time 600 ;=0D
> # }=0D
> =0D
> lease {=0D
> interface "eth0";=0D
> fixed-address 192.168.15.195;=0D
> medium "link0 link1";=0D
> option host-name "fixed add eth0";=0D
> option subnet-mask 255.255.240.0;=0D
> option broadcast-address 192.168.15.255;=0D
> option routers 192.168.15.195;=0D
> option domain-name-servers 192.168.15.195;=0D
> # renew 0 2007/2/3 00:00:01; // i also want to know @ these three=0D
> statement=0D
> # rebind 0 2007/2/3 00:00:01;=0D
> expire 0 2007/2/3 00:00:01;=0D
> }=0D
> =0D
> lease {=0D
> interface "eth1";=0D
> fixed-address 192.168.15.197;=0D
> option host-name "fixed add eth1";=0D
> option subnet-mask 255.255.240.0;=0D
> option broadcast-address 192.168.15.255;=0D
> option routers 192.168.15.197;=0D
> option domain-name-servers 192.168.15.197;=0D
> # renew 0 2007/2/3 00:00:01;=0D
> # rebind 0 2007/2/3 00:00:01;=0D
> expire 0 2007/2/3 00:00:01;=0D
> }=0D
> =0D
> =0D
> =0D
> =0D
> =0D
> thanks ............................=0D
> waiting for ur
> reply......................................=0D
> =0D
> Hitesh Sharma=0D
> =0D
> =0D
> =0D
> =0D
> =0D
> =0D
> =0D
> =0D
> =0D
> -------Original Message-------=0D
> =0D
> From: dhcp-users at isc.org=0D
> Date: 02/13/07 04:39:17=0D
> To: dhcp-users at isc.org=0D
> Subject: Re: related to leases...........need help plzz....=0D
> =0D
> hitesh sharma wrote:=0D
> =0D
> >actualiy , i want to know that ,=0D
> >1> when i am using fixed address (leases statement inside the .conf
> fil=
> e),=0D
> >then how to limit this address , i.e. if i want to use fixed address
> at=0D
> >certain time?=0D
> =0D
> Not sure what the question is. Are you asking for conditional=0D
> allocation, eg "client X can have address a.b.c.d but only between=0D
> 9am and 5pm" ?=0D
> =0D
> Firstly, I am not aware of any DHCP server offering any such=0D
> function, and in any case it would be non trivial to implement - each=0D
> time the client renews a lease you would have to compute the time the=0D
> lease is to remain valid and offer a lease that does not exceed that=0D
> time. Certainly a lot more work than "is the time within the=0D
> specified time window".=0D
> =0D
> Remember that DHCP is NOT a security protocol, it is trivial to=0D
> bypass such restrictions by manually configuring a client. If you=0D
> need to restrict use of systems, then there are generally better ways=0D
> of doing it.=0D
> =0D
> >2> if , i want that , if my machine is using fixed address , but=0D
> >when any server comes inro lan , it should detect that server , and=0D
> >produce request for leases.=0D
> =0D
> No, or at least not 'out of the box'. The server does not broadcast=0D
> it's presence, it is up to the client to ask. Yes it would be=0D
> possible to configure a system to repeatedly attempt to lease an=0D
> address and switch between the dhcp lease and another statically=0D
> configured address depending on whether you get a reply - but that=0D
> defeats the object of dhcp which is to reduce or eliminate=0D
> configuration of clients. What you are asking for would significantly=0D
> increase the administrative burden of managing clients.=0D
> =0D
> What many clients DO support is dynamically allocated "link local"=0D
> addresses - ie they will attempt to obtain a lease by dhcp, but if=0D
> they fail then they will allocate themselves an address in the=0D
> reserved "link local" range. If a dhcp server comes onto the network,=0D
> then (normally) these clients will get a lease because the client=0D
> will keep broadcasting for a dhcp server every few minutes. This is=0D
> entirely client specific and has no effect whatsoever on the dhcp=0D
> server.=0D
> =0D
> > 3> In case of fixed address, the renew , expire and rebind
> statement=
> is=0D
> >compulsory ? can i declare leases statement without that ? if not ,=0D
> >then what is significance of them?=0D
> =0D
> Can you clarify the question ?=0D
> =0D
> In general, there are no mandatory configuration options for the=0D
> client, and very few for the server.=0D
> =0D
> >4> i face one more problem , when i release the one of the leases=0D
> >(eth0/eth1), by using -r flag , then after sometime , it also take=0D
> >the leases=0D
> >from server. so , how to avoid leases , when one of the or both=0D
> >interface don't want leases , but even need to be in lan?=0D
> =0D
> Sorry, I don't understand the question.=0D
> =0D
> >6> when i m releasing the lease , and i want message related to=0D
> >that ie. message no. 7 , then , how to get it ?=0D
> =0D
> =0D
> =0D
> >7> in /var/lib/dhcp , in .leases file , it will comntain all
> leases=
> ,=0D
> >or only those are valid ?=0D
> =0D
> It may well contain older records as well.=0D
> =0D
> >8> we know that , at the 50 % time of leases, client try the=0D
> >renew it if it successes in that , remaining 50% leases first=0D
> >will use by client then new allocated leases , or , client will use=0D
> >new leases , n but remaining 50% leases in leases database.=0D
> =0D
> Once a new lease is issued, the expiry time of the previous lease is=0D
> irrelevant, the new expiry time is whatever the server offers in the=0D
> new lease - this can be (if the configuration has changed) shorter=0D
> than the previous one !=0D
> =0D
> Eg, suppose lease time is set to 4 days, and client is started at 9am=0D
> Monday, it will get a lease expiring at 9am Friday. Suppose=0D
> administrator changes lease time to 1 day after this lease is issued,=0D
> this will NOT affect the clients exiting lease. At 9am on Wednesday=0D
> (after 2 days, 50% of the original lease time), the client will renew=0D
> the lease, the server will offer it a 1 day lease, and if the client=0D
> accepts it, it will now have a lease expiring at 9am Thursday.=0D
> =0D
> If the config had not been changed, then the new lease would also be=0D
> for 4 days and would expire 9am Sunday.=0D
> =0D
> Bear in mind that the 50% time for attempting a renewal is only a=0D
> default, and may also be client specific
>
>
>
>
>
>
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