DHCP client questions

Michael Powell nightrecon at hotmail.com
Mon Sep 21 04:22:04 UTC 2009

Mel Flynn wrote:

> On Sunday 20 September 2009 21:19:28 stan wrote:
>> I have several machines (such as a mailserver) which _MUST_ have fixed
>> names. I have played around with /etc/dhcllient.conf, but not managed to
>> get this working. I can get IP addresses, and various things such as
>> default routers, and DNS servers, but I have not managed to get the
>> suggested name put in their DNS.
> Ok, I know you're trying to make clear what your problem is, but it's
> still not. So, let's try step by step,, using a FreeBSD mailserver as the
> example: 1) Does the mailserver have a fixed HOSTNAME or can the HOSTNAME
> change if the DHCP server wants it to?
> 2) When you say "but I have not managed to get the suggested name put in
> their DNS", does this mean you expect the FreeBSD mailserver to enter
> itself into the Microsoft DNS? Or can you not get the FreeBSD mailserver
> to name itself according to what the DHCP server tells them to?

Don't seem to have all the details either, but from what little I can piece 
together is his company being bought by another necessitates the melding of 
his old systems with the new companies' Windows based environment. This 
could very well be an incorrect assumption on my part.

In a Windows environment when DHCP is used, as it hands out IP addresses it 
then updates the IP/hostname pair in the DNS server database. This is 
configured to operate by the admins. Usually there are at least two DHCP 
scopes minimum for the dynamically assigned IPs, but there can also be 
configured a scope for static IPs for things such as mail servers. So it is 
still possible for a mail server to initialize networking via DHCP and be 
assigned the same statically assigned IP every time. It is the 
responsibility of the Windows DHCP servers to sync with the DNS server 
database. If you are not going to have static services such as a mail server 
initialize via DHCP then a system admin will have to manually enter this 
information into the DNS server database. Without possessing the 
administrative authority to do this things will get very frustrating.

Bottom line is, if what I think is going on is correct, he can fight this 
battle in myriad different directions but inevitably all will lead back to 
the system admins of the purchasing company must get involved in order to 
properly meld the 2 networks together. All 10,000 different paths which can 
be pursued will ultimately lead back to this, so they ought to just bite the 
bullet and get it over with.

(If one wants to run his own Unix based DNS servers so as to have this under 
his/her control set up for file based zone transfer from the Windows DNS 
servers. The key to making this work is to manually config the zone 
transfers on the Windows DNS machines to ascii instead of UTF8 or else the 
Unix box DNS zone files will be endlessly polluted with garbage characters. 
Of course this all is moot if you are not allowed to be delegated or be 
authoritative for your little piece of the DNS tree. Here again, this is 
still going to have to be handled by the purchasing companies' admins as 
they are the ones in the drivers seat. This type of melding of heterogeneous 
systems absolutely requires both sides to work together.) 


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