dhclient: ISP's server won't answer unicast DHCPREQUEST anymore

[Jiri Popelka]

On 12/12/2011 01:02 PM, Steve Clark wrote:
> On 12/12/2011 03:15 AM, Jordan Russell wrote:
>> A bizarre problem has appeared after upgrading from Fedora 14 to 15,
>> which brought dhclient from 4.2.0-P2 to 4.2.1-P1.
>>
>> Since the upgrade (weeks ago), my ISP's DHCP server no longer responds
>> to any of the unicast DHCPREQUEST packets sent by dhclient when it
>> enters the RENEWING state. However, hours later, when dhclient reaches
>> the REBINDING state and broadcasts instead, the server responds
>> immediately, and the renewal succeeds.
>>
>>    DHCPREQUEST on eth1 to 10.72.0.1 port 67
>>    DHCPREQUEST on eth1 to 10.72.0.1 port 67
>>    DHCPREQUEST on eth1 to 10.72.0.1 port 67
>>    [...]
>>    DHCPREQUEST on eth1 to 255.255.255.255 port 67
>>    DHCPACK from 10.72.0.1
>>    bound to 76.x.x.x -- renewal in 14685 seconds.
>>
>> tcpdump confirms that the unicast DHCPREQUEST packets are making it out
>> (with correct IP and MAC addresses), but no corresponding responses are
>> coming in.
>>
>> Was there any change in dhclient 4.2.1 that might explain this? I'm
>> using an empty dhclient.conf file just as I was prior to the upgrade.
>> (Initially, Fedora 15 inserted dhcp-client-identifier and hostname
>> settings into the config, but I've since removed both of those and
>> restarted dhclient numerous times.)
>>
>> Also, as an interim workaround to cut back on the syslog spam, is there
>> some way to force dhclient to broadcast all DHCPREQUEST packets (i.e.
>> skip the RENEWING state)?
>>
>> Thanks.
> I see the same behavior on Fedora 12 with
> dhclient-4.1.1-18.P1.fc12.x86_64
>
> ...
> Dec 11 06:01:41 joker dhclient[1829]: DHCPREQUEST on eth0 to 
> 10.99.32.1 port 67
> ...
> Dec 11 06:02:23 joker dhclient[1829]: DHCPREQUEST on eth0 to 
> 255.255.255.255 port 67
> Dec 11 06:02:23 joker dhclient[1829]: DHCPACK from 10.99.32.1
> Dec 11 06:02:23 joker dhclient[1829]: bound to xxx.xxx.xxx.66 -- 
> renewal in 4264 seconds.

I don't remember seeing this with previous versions,
but it works with dhclient-4.2.3-4.P1.fc16.x86_64 (Fedora 16) for me.
Dec 12 08:32:15 zepelin dhclient[1497]: DHCPREQUEST on br0 to 
10.34.xxx.y port 67
Dec 12 08:32:15 zepelin dhclient[1497]: DHCPACK from 10.34.xxx.y
Dec 12 08:32:17 zepelin dhclient[1497]: bound to 10.34.24.zz -- renewal 
in 34601 seconds.

--
Jiri
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