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Today's Topics:
1. Re: Dhcpd randomly returns the IP address or the backup IP
(glenn.satch...@uniq.com.au)
2. Re: DDNS updates for zone having multiple primary servers
(kraishak)
3. Re: DDNS updates for zone having multiple primary servers
(glenn.satch...@uniq.com.au)
----------------------------------------------------------------------
Message: 1
Date: Tue, 30 Mar 2021 10:14:55 +1100
From: glenn.satch...@uniq.com.au
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Dhcpd randomly returns the IP address or the backup IP
Message-ID: <dfba64c6f1fb19a44282ecfcd7aca...@uniq.com.au>
Content-Type: text/plain; charset=US-ASCII; format=flowed
The on-disk leases file is just a representation of what is in memory -
that is the true status, so as soon as it is released it would be marked
so in the in memory copy. I don't think timing would affect that. What
Sten says though about the history in the leases file is correct - each
new operation is appended to the file, so you can see previous ones, at
least for the life of the file. My understanding is that the file is
re-written every hour to preven tit growing too large. The previous file
remains dhcpd.leases~ so between the two you can get up to 2 hours of
history.
When a lease is released, it is marked as available. Given this
particular client has had both IPs in the past, then the matching
algorithm to find a new lease could come up with both possibilities.
Without looking at the code I wouldn't know precisely how it decides
upon a particular lease from the list of candidates. The client should
be prepared to switch IPs upon release of the lease and subsequent
discover. That is not the same as renewing an existing lease. I guess
the real problem is that DNS is not being updated.
Packet capture between dhcpd and the DNS server will at least show if
updates are being sent and you can then narrow it down to a problem with
either server.
regards,
Glenn
On 2021-03-30 03:26, Sten Carlsen wrote:
> Hi
>
> These two addresses are both in the same pool, so nothing illegal is
> happening. It is still odd that it sometimes gets one address and then
> the other, this should not happen.
>
> Consider the leases file as a historical document, each time something
> happens, the leases file gets added to. Once in a while it gets
> regenerated with just the current status of all leases.
>
> So for this sequence of events you should be able to reconstruct what
> happened by looking into this file.
>
> One thing that comes to mind is timing. The release and the discover
> happens in the same second, so what if the server could not write to
> the leases file before being asked about a new lease - this is not
> extending an existing lease as the discover indicates that the device
> does not have an address at this moment.
>
> Would it be possible to add a pause of a few seconds between the
> release and the discover? at least for an experiment. If that works,
> some timing is at the bottom of this.
>
> Possibly a wireshark trace could reveal the exact timing of these two
> messages.
>
> The leases file snippet did also not have both addresses as active,
> which could uncover other interesting things.
>
> --
> Best regards
> Sten Carlsen
>
> A pessimist is a person that can find a problem for every solution.
>
>> On 29 Mar 2021, at 12.05, Wayne Gemmell | Connect
>> <wa...@connect-mobile.co.za> wrote:
>>
>> Hi Sten
>>
>> One of the host I've been testing with in the kannel pool alternates
>> between the following
>>
>> inet 10.3.2.36/16 [1]
>>
>> inet 10.3.2.60/16 [2]
>>
>> Leases look as follows. I don't really understand why each would be
>> both free and active.
>>
>> Here's the log file of the responsible peer:
>> https://pastebin.com/UP6M1Lic
>>
>> DHCP Lease list on responsible peer. The other one has similar data
>> but no host names. https://pastebin.com/WX3NwkM2
>> Here's snippet of the lease file https://pastebin.com/fKFiZpQ0
>>
>> [3]
>>
>> On Fri, 26 Mar 2021 at 19:32, Sten Carlsen <st...@s-carlsen.dk>
>> wrote:
>>
>> Thanks
>>
>> Sten
>>
>> On 26 Mar 2021, at 08.43, Wayne Gemmell | Connect
>> <wa...@connect-mobile.co.za> wrote:
>>
>> Thanks Sten
>>
>> I've moved my class out of the subnet and the issue still persists.
>>
>> Well, that is one can of worms out of the picture.
>>
>> What are the two addresses?
>>
>> [3]
>>
>> On Thu, 25 Mar 2021 at 17:51, Sten Carlsen <st...@s-carlsen.dk>
>> wrote:
>>
>> You define the class kannel inside the subnet, so if there are any
>> other subnets, it will be defined there as well. Class definitions
>> are global always, defining them inside a subnet may have some
>> "interesting" side effects as some options are taken from that
>> subnet even if the host gets an address in a different subnet -
>> routers is one of them.
>>
>> So one thought is, if the backup address is not in this subnet, the
>> host will be given incorrect information.
>>
>> --
>> Best regards
>> Sten Carlsen
>>
>> --------------------------------------------------
>> Aoccdrnig to rseerach at Cmabrigde Uinervtisy,
>> it deosn't mttaer in waht oredr the ltteers in a
>> wrod are, the olny iprmoatnt tihng is taht the
>> frist and lsat lteter be at the rghit pclae.
>> The rset can be a ttoal mses and you can slitl
>> raed it wotihut porbelm. Tihs is bcuseae the
>> hmuan mnid deos not raed ervey lteter by istlef,
>> but the wrod as a wlohe. Amzanig, huh?
>> --------------------------------------------------
>>
>> On 25 Mar 2021, at 13.01, Wayne Gemmell | Connect
>> <wa...@connect-mobile.co.za> wrote:
>>
>> I tried it. No change. The issue still persists.
>>
>> [3]
>>
>> On Tue, 23 Mar 2021 at 16:19, Wayne Gemmell | Connect
>> <wa...@connect-mobile.co.za> wrote:
>>
>> I'll give it a try, thanks.
>>
>> [3]
>>
>> On Tue, 23 Mar 2021 at 01:32, Bill Shirley
>> <b...@c3po.polymerindustries.biz> wrote:
>>
>> Try:
>> update-optimization off;
>>
>> Bill
>> On 3/19/2021 2:22 AM, Wayne Gemmell | Connect wrote:
>>
>> Hi
>>
>> When my dhcp server gets a DHCPRELEASE followed by a DHCPDISCOVER
>> then it randomly allocates the IP address or the backup IP address
>> that are assigned to the host in the lease file to the host. The
>> assignments always got to the correct host and the mac address
>> doesn't change.
>>
>> When this backup IP address is allocated then dynamic DNS isn't
>> updated and my container is unreachable.
>>
>> I've put all the relevant details in the link below but am more than
>> happy enough to furnish anything that is missing. Can anyone help
>> please?
>>
>> https://gitlab.isc.org/isc-projects/dhcp/-/issues/172 [4]
>>
>> [3]
>>
>> _______________________________________________
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>> subscriptions. Contact us at https://www.isc.org/contact/ for more
>> information.
>>
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>>
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>>
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>
> Links:
> ------
> [1] http://10.3.2.36/16
> [2] http://10.3.2.60/16
> [3] https://connect-mobile.co.za/mobile_marketing_solutions/
> [4] https://gitlab.isc.org/isc-projects/dhcp/-/issues/172
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------------------------------
Message: 2
Date: Mon, 29 Mar 2021 23:00:19 -0500 (CDT)
From: kraishak <kraishak....@gmail.com>
To: dhcp-users@lists.isc.org
Subject: Re: DDNS updates for zone having multiple primary servers
Message-ID: <1617076819943-0.p...@n4.nabble.com>
Content-Type: text/plain; charset=us-ascii
Hi Simon,
Thanks for the information, Just want to cross check does it means can we
configure the secondary appliance as comma separated IP's as below if we
have more than one ?
zone example.com.
{
primary 192.168.0.45;
secondary 192.168.0.47,192.168.0.48;
}
2)I have one more doubt while configuring the DDNS updates
we have an option domain-name-servers and zone servers like below
option domain-name-servers <Server1>, <Server2>;
zone example.com.
{
primary <ServerZ1>;
secondary <ServerZ2>;
}
Does Server1, server2 should be same as ServerZ1, ServerZ2?
Thanks in Advance
Kraishak
--
Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
------------------------------
Message: 3
Date: Tue, 30 Mar 2021 15:53:13 +1100
From: glenn.satch...@uniq.com.au
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: DDNS updates for zone having multiple primary servers
Message-ID: <e11857d310f753a7d6b09d2e01811...@uniq.com.au>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Kraishak
option domain-name-servers <Server1>, <Server2>;
This sets the list of DNS servers to be used by the client for looking
up DNS entries. It is not related to DDNS updates. In a large network,
for example, you may want this to point to local DNS servers. If your
authoritative DNS only lists public IPs then you might want to point to
the Google DNS (8.8.8.8, etc) on the clients.
For the zone setting, have you had a look at the dhcpd.conf man page, in
particular the section titled "DYNAMIC DNS UPDATE SECURITY" where it
explains the syntax and behaviour.
It's not clear whether it is a comma separated list of secondaries, or
multiple secondary statements with a single address.
regards,
Glenn
On 2021-03-30 15:00, kraishak wrote:
> Hi Simon,
>
> Thanks for the information, Just want to cross check does it means can
> we
> configure the secondary appliance as comma separated IP's as below if
> we
> have more than one ?
>
> zone example.com.
> {
> primary 192.168.0.45;
> secondary 192.168.0.47,192.168.0.48;
> }
>
> 2)I have one more doubt while configuring the DDNS updates
> we have an option domain-name-servers and zone servers like below
> option domain-name-servers <Server1>, <Server2>;
> zone example.com.
> {
> primary <ServerZ1>;
> secondary <ServerZ2>;
> }
> Does Server1, server2 should be same as ServerZ1, ServerZ2?
>
> Thanks in Advance
> Kraishak
>
>
>
>
>
> --
> Sent from: http://isc-dhcp-users.2343191.n4.nabble.com/
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
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> dhcp-users@lists.isc.org
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