samba - Nov 2015 - Authentication to Secondary Domain Controller initially fails when PDC is offline

Mathias, thank you very much for your comprehensive instructions!

Just one question: Harry suggested that, in order to overcome the below 
DNS related problems, the TTL would have to be adjusted (lowered). 
However, the TTL seems to be the only time value not covered by the 
command provided by you.

Is it really the TTL that is the culprit or is it rather the first time 
value (something like "Refresh value" in english)?

Do you know this?

Ole


Am 19.11.2015 um 11:19 schrieb mathias dufresne:
> Hi Ole,
>
> You want to change SOA of your AD domain?
>
> Here some working command:
> samba-tool dns update <working DC> samba.domain.tld \
> samba.domain.tld SOA \
> 'oldSOA.samba.domain.tld. hostmaster.samba.domain.tld. 58 900 600 
> 86400 3600' \
> 'newSOA.samba.domain.tld. hostmaster.saba.domain.tld. 59 900 600 86400 
> 3600' -k yes
>
> This needs you performed some kinit before using an account able to 
> modify this entry (by default only administrator is able to that I 
> expect).
>
> This must be done for the two DNS zones of your domain:
> samba.domain.tld + _msdcs.samba.domain.tld
>
> First number of replacement record (here "59") is serial number. 
> Replication of change seemed to work without changing that serial 
> number but as DNS love to rely on it, changing that serial should be a 
> good idea.
>
> Hoping this helps...
>
> Cheers,
>
> mathias
>
>
> 2015-11-18 16:44 GMT+01:00 Ole Traupe <ole.traupe at tu-berlin.de 
> <mailto:ole.traupe at tu-berlin.de>>:
>
>
>         It is DNS related.
>
>             What is the best way of dealing with this?
>
>         The *best way* is a HA solution for your DNS Servers, but its
>         expensive.
>
>         The DNS client (resolver) caches the srv records for 15
>         minutes aka 900
>         seconds.
>
>         ipconfig /flushdns drops the cache. Reboot does the same.
>
>         On server side you may set shorter TTL for the server records,
>         but then
>         you have more DNS traffic. On small netwoks (sites up to 20
>         clients, no
>         wifi) I have good experience with a TTL of 180.
>
>
>     Harry, I tried this - unsuccessfully.
>
>     I have TTL settings in a) the SOA and b) the NS record of the FQDN
>     and the _msdcs.FQDN sections in my Windows RSAT DNS console. None
>     of these 4 entries I can change: I get something like "The Source
>     Of Authority (SOA) cannot be updated. The record already exists."
>
>     Do you have an idea how to accomplish this? Currently the setting
>     is 1h, which is pretty long.
>
>     Ole
>
>
>
>
>     -- 
>     To unsubscribe from this list go to the following URL and read the
>     instructions: https://lists.samba.org/mailman/options/samba
>
>

No idea about your main issue, I was merely answering to your last question
about changing SOA record.

Here is another view of that command:
samba-tool dns update <server> <zone> <name> SOA \
'OLDnameserver email serial refresh retry expire minimumttl' \
'NEWnameserver email serial refresh retry expire minimumttl'

I'm not too confident with DNS internals so I'm not sure if the TTL you
mentioned is or isn't "expire" or "minimumttl".

After digging a little bit it seems previous line is completely wrong,
neither "expire" nor "minimumttl" are "TTL".
This because :
dig -t SOA SAMBADOMAIN.TLD
...
samba.domain.tld. 1715 IN      SOA     DC1.samba.domain.tld. 62 900 600
86400 3600
...

And from what I just read in dig "ANSWER SECTION" the second field is
the
TTL, so 1715 in my case, which as nothing to do with "expire" (86400)
or
"minimumtll" (3600).

And that makes me wondering how TTL can be less than "minimumttl"...

So, the short way: the command I gave do not seem to be designed to help
you changing TTL. Sorry : )

Cheers,

mathias

2015-11-19 13:43 GMT+01:00 Ole Traupe <ole.traupe at tu-berlin.de>:
> Mathias, thank you very much for your comprehensive instructions!
>
> Just one question: Harry suggested that, in order to overcome the below
> DNS related problems, the TTL would have to be adjusted (lowered). However,
> the TTL seems to be the only time value not covered by the command provided
> by you.
>
> Is it really the TTL that is the culprit or is it rather the first time
> value (something like "Refresh value" in english)?
>
> Do you know this?
>
> Ole
>
>
>
> Am 19.11.2015 um 11:19 schrieb mathias dufresne:
>
> Hi Ole,
>
> You want to change SOA of your AD domain?
>
> Here some working command:
> samba-tool dns update <working DC> samba.domain.tld \
> samba.domain.tld SOA \
> 'oldSOA.samba.domain.tld. hostmaster.samba.domain.tld. 58 900 600 86400
> 3600' \
> 'newSOA.samba.domain.tld. hostmaster.saba.domain.tld. 59 900 600 86400
> 3600' -k yes
>
> This needs you performed some kinit before using an account able to modify
> this entry (by default only administrator is able to that I expect).
>
> This must be done for the two DNS zones of your domain:
> samba.domain.tld + _msdcs.samba.domain.tld
>
> First number of replacement record (here "59") is serial number.
> Replication of change seemed to work without changing that serial number
> but as DNS love to rely on it, changing that serial should be a good idea.
>
> Hoping this helps...
>
> Cheers,
>
> mathias
>
>
> 2015-11-18 16:44 GMT+01:00 Ole Traupe <ole.traupe at tu-berlin.de>:
>
>>
>> It is DNS related.
>>>
>>> What is the best way of dealing with this?
>>>>
>>> The *best way* is a HA solution for your DNS Servers, but its
expensive.
>>>
>>> The DNS client (resolver) caches the srv records for 15 minutes aka
900
>>> seconds.
>>>
>>> ipconfig /flushdns drops the cache. Reboot does the same.
>>>
>>> On server side you may set shorter TTL for the server records, but
then
>>> you have more DNS traffic. On small netwoks (sites up to 20
clients, no
>>> wifi) I have good experience with a TTL of 180.
>>>
>>
>> Harry, I tried this - unsuccessfully.
>>
>> I have TTL settings in a) the SOA and b) the NS record of the FQDN and
>> the _msdcs.FQDN sections in my Windows RSAT DNS console. None of these
4
>> entries I can change: I get something like "The Source Of
Authority (SOA)
>> cannot be updated. The record already exists."
>>
>> Do you have an idea how to accomplish this? Currently the setting is
1h,
>> which is pretty long.
>>
>> Ole
>>
>>
>>
>>
>> --
>> To unsubscribe from this list go to the following URL and read the
>> instructions:  https://lists.samba.org/mailman/options/samba
>>
>
>
>

Ok, I see. Nevertheless, thank you very much for your effort!

I must say that I can't actually believe that no one knows an answer to 
this problem. It must affect MANY people using Samba DCs. According to 
all the tests on the wiki, everything is working fine. Then I pull the 
plug on my first DC and no one can log on. And this time I waited far 
longer than the suggested "refresh interval" of 15 min - even longer 
than the value called "TTL" in the GUI of 1h. I also tried
"ipconfig
/flushdns" on my windows client. Does not improve the situation. Only a 
reboot solves the issue. But that would be no acceptable practice for 
Linux member servers. And it doesn't seem to help, anyway (just tried this).

It is one of the first and most important tests for a domain to see what 
happens if the first DC is down. Without a working take-over, other DCs 
are nothing more than backup (replication) targets, and the domain is 
not fail-safe.

This can't be the end of the story, right?

Ole



Am 19.11.2015 um 14:04 schrieb mathias dufresne:
> No idea about your main issue, I was merely answering to your last 
> question about changing SOA record.
>
> Here is another view of that command:
> samba-tool dns update <server> <zone> <name> SOA \
> 'OLDnameserver email serial refresh retry expire minimumttl' \
> 'NEWnameserver email serial refresh retry expire minimumttl'
>
> I'm not too confident with DNS internals so I'm not sure if the TTL
> you mentioned is or isn't "expire" or "minimumttl".
>
> After digging a little bit it seems previous line is completely wrong, 
> neither "expire" nor "minimumttl" are "TTL".
> This because :
> dig -t SOA SAMBADOMAIN.TLD
> ...
> samba.domain.tld. 1715 IN      SOA DC1.samba.domain.tld. 62 900 600 
> 86400 3600
> ...
>
> And from what I just read in dig "ANSWER SECTION" the second
field is
> the TTL, so 1715 in my case, which as nothing to do with "expire"
> (86400) or "minimumtll" (3600).
>
> And that makes me wondering how TTL can be less than
"minimumttl"...
>
> So, the short way: the command I gave do not seem to be designed to 
> help you changing TTL. Sorry : )
>
> Cheers,
>
> mathias
>
> 2015-11-19 13:43 GMT+01:00 Ole Traupe <ole.traupe at tu-berlin.de 
> <mailto:ole.traupe at tu-berlin.de>>:
>
>     Mathias, thank you very much for your comprehensive instructions!
>
>     Just one question: Harry suggested that, in order to overcome the
>     below DNS related problems, the TTL would have to be adjusted
>     (lowered). However, the TTL seems to be the only time value not
>     covered by the command provided by you.
>
>     Is it really the TTL that is the culprit or is it rather the first
>     time value (something like "Refresh value" in english)?
>
>     Do you know this?
>
>     Ole
>
>
>
>     Am 19.11.2015 um 11:19 schrieb mathias dufresne:
>>     Hi Ole,
>>
>>     You want to change SOA of your AD domain?
>>
>>     Here some working command:
>>     samba-tool dns update <working DC> samba.domain.tld \
>>     samba.domain.tld SOA \
>>     'oldSOA.samba.domain.tld. hostmaster.samba.domain.tld. 58 900
600
>>     86400 3600' \
>>     'newSOA.samba.domain.tld. hostmaster.saba.domain.tld. 59 900
600
>>     86400 3600' -k yes
>>
>>     This needs you performed some kinit before using an account able
>>     to modify this entry (by default only administrator is able to
>>     that I expect).
>>
>>     This must be done for the two DNS zones of your domain:
>>     samba.domain.tld + _msdcs.samba.domain.tld
>>
>>     First number of replacement record (here "59") is serial
number.
>>     Replication of change seemed to work without changing that serial
>>     number but as DNS love to rely on it, changing that serial should
>>     be a good idea.
>>
>>     Hoping this helps...
>>
>>     Cheers,
>>
>>     mathias
>>
>>
>>     2015-11-18 16:44 GMT+01:00 Ole Traupe <ole.traupe at
tu-berlin.de
>>     <mailto:ole.traupe at tu-berlin.de>>:
>>
>>
>>             It is DNS related.
>>
>>                 What is the best way of dealing with this?
>>
>>             The *best way* is a HA solution for your DNS Servers, but
>>             its expensive.
>>
>>             The DNS client (resolver) caches the srv records for 15
>>             minutes aka 900
>>             seconds.
>>
>>             ipconfig /flushdns drops the cache. Reboot does the same.
>>
>>             On server side you may set shorter TTL for the server
>>             records, but then
>>             you have more DNS traffic. On small netwoks (sites up to
>>             20 clients, no
>>             wifi) I have good experience with a TTL of 180.
>>
>>
>>         Harry, I tried this - unsuccessfully.
>>
>>         I have TTL settings in a) the SOA and b) the NS record of the
>>         FQDN and the _msdcs.FQDN sections in my Windows RSAT DNS
>>         console. None of these 4 entries I can change: I get
>>         something like "The Source Of Authority (SOA) cannot be
>>         updated. The record already exists."
>>
>>         Do you have an idea how to accomplish this? Currently the
>>         setting is 1h, which is pretty long.
>>
>>         Ole
>>
>>
>>
>>
>>         -- 
>>         To unsubscribe from this list go to the following URL and
>>         read the
>>         instructions: https://lists.samba.org/mailman/options/samba
>>
>>
>
>

Although I don't know what "dig" actually means, I was able to dig
up
the following for my SOA:

my.domain.tld.       3600    IN      SOA     DC2.my.domain.tld. 
hostmaster.my.domain.tld. 29 180 600 86400 180

This is after I reduced refresh interval and minimum TTL to 3 min (180 
s). Still, the TTL of the SOA itself is 1h (3600 s).

This strongly suggests, that the TTL for DNS info *provided by* the SOA 
is not necessarily related to the TTL of the SOA record *itself*.

Might that be? Could that be the reason why reducing minimum TTL doesn't 
solve the login problem? How to change the TTL of the SOA record? Does 
that even make sense?

Nevertheless, I want to re-state that waiting longer than the TTL of 1h 
after pulling the (Ethernet) plug on my first DC didn't improve the 
situation, either.

Ole


Am 19.11.2015 um 14:04 schrieb mathias dufresne:
> No idea about your main issue, I was merely answering to your last 
> question about changing SOA record.
>
> Here is another view of that command:
> samba-tool dns update <server> <zone> <name> SOA \
> 'OLDnameserver email serial refresh retry expire minimumttl' \
> 'NEWnameserver email serial refresh retry expire minimumttl'
>
> I'm not too confident with DNS internals so I'm not sure if the TTL
> you mentioned is or isn't "expire" or "minimumttl".
>
> After digging a little bit it seems previous line is completely wrong, 
> neither "expire" nor "minimumttl" are "TTL".
> This because :
> dig -t SOA SAMBADOMAIN.TLD
> ...
> samba.domain.tld. 1715 IN      SOA DC1.samba.domain.tld. 62 900 600 
> 86400 3600
> ...
>
> And from what I just read in dig "ANSWER SECTION" the second
field is
> the TTL, so 1715 in my case, which as nothing to do with "expire"
> (86400) or "minimumtll" (3600).
>
> And that makes me wondering how TTL can be less than
"minimumttl"...
>
> So, the short way: the command I gave do not seem to be designed to 
> help you changing TTL. Sorry : )
>
> Cheers,
>
> mathias
>
> 2015-11-19 13:43 GMT+01:00 Ole Traupe <ole.traupe at tu-berlin.de 
> <mailto:ole.traupe at tu-berlin.de>>:
>
>     Mathias, thank you very much for your comprehensive instructions!
>
>     Just one question: Harry suggested that, in order to overcome the
>     below DNS related problems, the TTL would have to be adjusted
>     (lowered). However, the TTL seems to be the only time value not
>     covered by the command provided by you.
>
>     Is it really the TTL that is the culprit or is it rather the first
>     time value (something like "Refresh value" in english)?
>
>     Do you know this?
>
>     Ole
>
>
>
>     Am 19.11.2015 um 11:19 schrieb mathias dufresne:
>>     Hi Ole,
>>
>>     You want to change SOA of your AD domain?
>>
>>     Here some working command:
>>     samba-tool dns update <working DC> samba.domain.tld \
>>     samba.domain.tld SOA \
>>     'oldSOA.samba.domain.tld. hostmaster.samba.domain.tld. 58 900
600
>>     86400 3600' \
>>     'newSOA.samba.domain.tld. hostmaster.saba.domain.tld. 59 900
600
>>     86400 3600' -k yes
>>
>>     This needs you performed some kinit before using an account able
>>     to modify this entry (by default only administrator is able to
>>     that I expect).
>>
>>     This must be done for the two DNS zones of your domain:
>>     samba.domain.tld + _msdcs.samba.domain.tld
>>
>>     First number of replacement record (here "59") is serial
number.
>>     Replication of change seemed to work without changing that serial
>>     number but as DNS love to rely on it, changing that serial should
>>     be a good idea.
>>
>>     Hoping this helps...
>>
>>     Cheers,
>>
>>     mathias
>>
>>
>>     2015-11-18 16:44 GMT+01:00 Ole Traupe <ole.traupe at
tu-berlin.de
>>     <mailto:ole.traupe at tu-berlin.de>>:
>>
>>
>>             It is DNS related.
>>
>>                 What is the best way of dealing with this?
>>
>>             The *best way* is a HA solution for your DNS Servers, but
>>             its expensive.
>>
>>             The DNS client (resolver) caches the srv records for 15
>>             minutes aka 900
>>             seconds.
>>
>>             ipconfig /flushdns drops the cache. Reboot does the same.
>>
>>             On server side you may set shorter TTL for the server
>>             records, but then
>>             you have more DNS traffic. On small netwoks (sites up to
>>             20 clients, no
>>             wifi) I have good experience with a TTL of 180.
>>
>>
>>         Harry, I tried this - unsuccessfully.
>>
>>         I have TTL settings in a) the SOA and b) the NS record of the
>>         FQDN and the _msdcs.FQDN sections in my Windows RSAT DNS
>>         console. None of these 4 entries I can change: I get
>>         something like "The Source Of Authority (SOA) cannot be
>>         updated. The record already exists."
>>
>>         Do you have an idea how to accomplish this? Currently the
>>         setting is 1h, which is pretty long.
>>
>>         Ole
>>
>>
>>
>>
>>         -- 
>>         To unsubscribe from this list go to the following URL and
>>         read the
>>         instructions: https://lists.samba.org/mailman/options/samba
>>
>>
>
>