Re: DHCP
- From: "Bill Grant" <not.available@online>
- Date: Fri, 7 Oct 2005 10:43:51 +1000
The only way to know for sure would be to do this on a network and
monitor the traffic. My guess is that it will get its existing IP. I am
connected to a DHCP server with a 40 minute lease time. It renews after 20
minutes when online. Even if I am off for hours, I get the same IP when I
start up. When the client sends a DHCPDISCOVER, the server replies with an
offer of its old IP.
I suspect this would only change if that IP had already been reissued before
I booted up.
Poppen wrote:
> So as you said first I got a network cable unplugged , I wait for 10
> seconds and plug the cable back to the network.
> Will the NIC start the " dhcp discover process " all over again
> or
> Is it possible for that the NIC will request a renewal of its "OLD "
> IPaddress.
> Will DHCP positively identify the source ( MAC address of NIC card )
> and identify that this NIC card was " leased out the 10.0.0.25 "
> ipaddress and renew its lease.
> Because DHCP server will not lease the 10.0.0.25 IPaddress till its
> lease duration is over.
>
> Let me at this point make my real question.
> I have a client system with say Ipaddress 10.0.0.25 . I need to
> force the client to have a new ipaddress .
> I cannot do an ipconfig / release and renew as the client system is
> in a remote location and I am giving telephonic support.
> So what I did was
> 1) Make the DHCP lease of all the IP addresses to 1 minute at server.
> I wait for the client system to request a renew( originally lease
> renewal = 15 minutes ). The system would request after 7 minutrs
>
>> AFAIK the machine will revert to: cable not attached. and thus NOT
>> have an IP-Address.
>>
>> If you plug it into an other Switch with no DHCP server attached or
>> attach a loppback cable it wil revert to APIPA.
>>
>> good luck,
>>
>> Eric Denekamp
>> mailto:ericd@xxxxxxxxxxxxxxx
>>
>>> This is an academic question regarding the lease of Ip address by
>>> the DHCP
>>> server to clients.
>>> 1) the server has assigned an ip address 10.0.0.25 to the client A.
>>> The
>>> lease period is for 1 hour( this is a hypothetical lease period for
>>> the
>>> scenario ). Now if I dissconnect the network cable from the system,
>>> i do not
>>> shut it down.
>>> According to the dhcp lease, the client system will ask for renewal
>>> at 50% of lease period. Since cable is unplugged it will not be able
>>> to renew it. Now at the end of 1 hour the dhcp lease will expire.
>>>
>>> Now will the system automatically revert to APIPA ( 169.254.x.y ) as
>>> soon as
>>> the lease expires
>>> or
>>> Will the IPaddress expire to 0.0.0.0
>>> or
>>> Will the client retain the IP 10.0.0.25 , till the cable is plugged
>>> in and
>>> the NIC will request for a renewal.
.
- References:
- Re: DHCP
- From: Eric Denekamp
- Re: DHCP
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