From: Matt Reynolds (
Date: Wed Oct 20 1999 - 08:13:53 CDT

Well, it goes to show that if one doesn't specify the problem
the results aren't quite what one expects. So, the burden is mine to
be more accurate.
Thanks to all, but:
a. I know what DHCP means and is.
b. I know what DNS is.

What I am looking for is a means by which my NIS+ database
is updated when a DHCP request is responded to. The dhcpconfig even
alludes to the fact that DHCP will update the NIS+ database when it
out an IP address, but it doesn't! Sun acknowledges this problem - and
SO is now part of a general Enhance Request for DHCP to update NIS+
database (the response from Sun will be the end of this summary).

The reason I don't want to use DNS is:
a. my internal network space is unregistered and unknown to the DNS
in general - and I want to keep it that way. I use Network Address
and my external DNS is way different and seperate from my internal
Besides, I don't want my host names known to the external world for
b. I don't want to have to set up two different DNS spaces, one
internal, and a second for registered external!

I want my host to ip mapping internally to be done by NIS+. Yes, wins
is a
solution and works, but there are two unix host to ip mappings which are
and wins won't satisfy this. One is critical - Solstice backup (aka
Legato Networker)
uses host names only and depends on NIS+ to resolve the ip address.
this mapping, this backup fails! The other mapping is one of ease -
when running
x-windows on a pc - which we do often, it is easier to specify a pc name
an ip address.

There were a couple of suggestions which indicate that DHCP will update
a dynamic
DNS - but I want DHCP to update NIS+. So, I have to wait for Sun to do
this - which
they indicate they will *sometime*. In the mean time, I'm stuck with
pc clients with NIS+ and Solstice with fixed ip addresses.

The replies I received:

             Marc Summers <>
You want to go to and check out the documentation
on DHCP, you can do a search, or look up under solaris 7 documentation
and find all you ever wanted to know about DHCP and then some.

"Matthew Stier" <>

The DHCP protocol is as it's name implies. A "Dynamic Host
Protocol". It is for the configuration of Hosts, not Servers?

Even Microsoft doesn't tie DHCP and WINS together. It may seem like it,
but what is really happening, is that the client gets configured through

DHCP and then announces itself, and it is those announcements that

Now to be fair, there is a Dynamic DNS implementation available, which
be tied into most implementations of DHCP to obtain what you want; and I

believe Solaris 8 will ship with this.

"Jonathon W. Ross" <>


You are missing what DHCP is :)

Dynamic *HOST* Configuration Protocol.


Gwynne, Alun P" <
Hi Matt,
I wonder if you are confusing WINS, DNS and DHCP ? DHCP is for farming
IP configurations - addresses, gateways etc. It doesn't maintain a name

DHCP doesn't tell every client what name it should have, since they will

usually have names already. It gets a request from a hardware address,
issues the dynamic details. The only way that the issued details get
registered anywhere is with a dynamic name service like WINS or the
new Dynamic DNS.

When your Win98 (or any windows) client loads, it has to actively
itself with WINS. This is a flat namespace, belonging only to MS
If you want to register with a "proper" name service, you would have to
some software that detects what's going on, then dynamically updates the

name service. This is the gist of DDNS, but I haven't looked at NIS.


Peter Watkins <>
Yes, I hit this as well and have yet to find a sensible solution.
So if you find one I'll be grateful for any more information. In
fact I think this is a serious problem if you use Sendmail for
your email and have invoked the anti-third party relaying features.
In this case the sendmail tries to do a IP lookup on the connecting
PC and if it doesn't find a correct result promptly rejects the
connection. Naturally with DHCP running this is prone to fail!!!

Reading the literature I believe that hostname CAN be passed by
DHCP but not in a very straightforward manner. I'm still looking
at that.

I think that for the lookup problem what you need to do is put
your complete DHCP IP range into DNS/NIS/NIS+ with corresponding
hostnames. Then the lookup will always return the same hostname
for a given IP number. Which is what you want. It remains unclear
to me what hostname the client actually reports and whether this
is actually relevant.

Peter Watkins

"Shoshana B. Billik" <>

        Hi, Matt! Thanks for your message, which you sent to the
mailing list, about DHCP.

        I'm a newbie to this list, so I may not know what I'm talking
here, but it seems to me that it isn't the role of DHCP to provide IP
to hostname resolution; rather, I would think this service would be
provided by
NIS/NIS+ and/or DNS. I'm therefore wondering if the problem lies with
setup of the NIS+ server rather than with the DHCP server.

        I'll be curious to hear what answers others come up with. Take


Alan Orndorff <>
Microsoft's answer to this problem was WINS. Have you thought about
going to and grabbing DHCP and DDNS from them and
setting it up?


Nate Itkin ~ <>

DHCP is useful for laptops, diskless systems, and roving devices. It
allows someone to easily obtain an ip address on a short term basis.
A smart client (Solaris for example, but not M$ Windoze) can also
a hostname from DHCP as well as a laundry list of other useful
such as the ip address of netbios name server(s), the netmask, broadcast

address, default router, and so on. However, you still need to create
entry in the DNS and or NIS host table for each leased IP address (if
desire to have the forward name-to-ip mapping work). I guess the best
to think about DHCP is like BOOTP because that's really what DHCP is -
plus enhancements.

You might want to investigate the latest and greatest version of BIND.
It may offer some native DHCP support. I know it has been a topic of
discussion, but I don't know if anything has been done.

- Nate Itkin

"Darryl C. Price" <> My apologies in advance for the simplicity of this response. My intent most certainly is not to condescend, but ping and other tcp and udp applications still have to make calls to the resolver library to resolve the address. The purpose of DHCP is not to supplant DNS or NIS for name resolution. Its purpose is to eliminate some of the complexity

of managing your namespace via reusable dynamically allocated address/hostnames. If you have some fixed number of addresses you intend to dynamically assign you can define them in advance (DNS, NIS, etc ...) and never have to worry about them again. You DHCP server need

only maintain a database of available addresses in the address pool.

--Darryl --------------------------------------------------------------------------------------

Arthur Darren Dunham <>

DHCP is for many things. The main thing is providing a MAC address to IP address mapping. NT relies heavily on NT naming via WINS. The Microsoft NT DHCP server integrates these two items.

Most UNIX names are distributed via DNS. DNS is distributed and cached,

so fast updates from a single server are difficult.

There are some projects to attempt to make DNS and DHCP work together more closely, but those are in development.

If you need dynamic naming with the Sun DHCP server, you'd have to add on some scripts of your own to populate whatever naming scheme you're using (NIS/NIS+/DNS). --------------------------------------------------------------------------------------

"David Evans" <> DHCP allows _dynamic_ allocation of an IP address to an NIC address. This can then be allocated to another card when the first machine if finished with it (normally off-line or turned off). So hostname is not relevant except on the client end. The IP issued may not be the same each time. If you are only issuing the one IP address what are you doing run DHCP when a static is all that is required?

If you want to ping on hostname you need a _static_ IP.

I think you need to do some reading on DHCP and DNS. You seem to have the concepts slightly bent.

I'd give some pointers to the DHCP and DNS material but that area is not

my forte. Maybe your summary could contain a few pointers.

Hope this helps,

David Evans --------------------------------------------------------------------------------------

Erwin Fritz <>

DHCP is for IP address management, not host name resolution. If you want

host name resolution on Solaris, look at DNS. I don't know whether Sun's

DNS integrates with Sun's DHCP, though. --------------------------------------------------------------------------------------

Sun Response:

Hi Matt,

It looks like Sun's DHCP server currently doesn't have the functionality of dynamically updating the database (either through NIS+ or files) with the hostname of DHCP client. You would have to associate the IP address with a hostname and choose this option within the setup of the DHCP server to currently work around this. There have been many bugs filed against this issue, most closed as a duplicate of bug #4006121. I have added you to this bug. There's not much that can be done at this point other than waiting for the fix. These bugs have been filed as RFE's (Request for enhancement) because the DHCP server is following the RFC standard.

If you have any questions or need clarification, let me know. I'll leave this service order open through end of week (10/22).

Thanks, Kim McNeill (510) 574-8585 Sun Enterprise Services

Here's the bug report:

Bug Id: 4006121 Product: sunos Category: network Subcategory: dhcp_server Bug/Rfe/Eou: rfe Synopsis: We should add ability to have dhcp daemon update hosts information (optionally)

Description: When DNS dynamic update becomes available in Solaris, the in.dhcpd should be modified to allow update of the hosts tables (thru xfn), and thus update files, dns, or nisplus.

Example of other bugs filed:

Bug #4086938 (Synopsis: RFE to allow dhcp servers to update DNS/NIS+ with names from dhcp clients) This issue is closed as a duplicate of the above bug #4006121. =============================================================

Thanks to everyone for their replys! Matt Reynolds

-- Matt Reynolds IS/Network Manager V:303-415-6166 Aztek Engineering, Inc. F:303-786-9190 2477 55th St. Boulder, CO 80301

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