reverse name lookup & DHCP

reverse name lookup & DHCP

Post by eyeze » Fri, 26 Nov 1999 04:00:00



How does one deal with reverse name lookup in a DHCP environment?

Such as the problems with telnet etc. when their machines get their IP
address via DHCP.

A) they are not defined in DNS because their address changes...
B) they are not defined in hosts/lmhosts etc because of the same reason...

Would like some help with resolving this issue..

TIA

Keith

 
 
 

reverse name lookup & DHCP

Post by Steve Cowle » Sat, 27 Nov 1999 04:00:00



Quote:> How does one deal with reverse name lookup in a DHCP environment?

> Such as the problems with telnet etc. when their machines get their IP
> address via DHCP.

> A) they are not defined in DNS because their address changes...
> B) they are not defined in hosts/lmhosts etc because of the same reason...

> Would like some help with resolving this issue..

> TIA

> Keith

Even though DHCP clients addresses change, they must still be added to DNS zones. When I
setup DHCP servers and their associated scopes, I also add  the corresponding in-addr zone
to the DNS server.

If using "bind" I create names like...
dhcp0-1.mydomain.com  (192.168.0.1)
dhcp0-2.mydomain.com  (192.168.0.2)
etc... In the above example, the in-addr zone name does not match the actual FQDN of the
client or NETBIOS name. But at least  the reverse lookup can be done. At least until DDNS
(Dynamic DNS) is released.

If using MS DNS server, I will configure the zones to use WINS for in-addr lookups. That
way when a MS client (or even Samba client) logins it will register with the WINS server
which in turn makes a entry in the appropriate DNS zone (when a DNS query is received).
This is a pretty cool feature of MS DNS. I have personally had a lot of luck with this
configuration but the key is setting up the proper TTL's to match the DHCP scope
expiration dates. Obviously, the linux box's resolver must also be configured to use MS
DNS server. i.e. /etc/resolv.conf

Steve Cowles

 
 
 

reverse name lookup & DHCP

Post by eyeze » Sat, 27 Nov 1999 04:00:00





> > How does one deal with reverse name lookup in a DHCP environment?

> > Such as the problems with telnet etc. when their machines get their IP
> > address via DHCP.

> > A) they are not defined in DNS because their address changes...
> > B) they are not defined in hosts/lmhosts etc because of the same
reason...

> > Would like some help with resolving this issue..

> > TIA

> > Keith

> Even though DHCP clients addresses change, they must still be added to DNS
zones. When I
> setup DHCP servers and their associated scopes, I also add  the

corresponding in-addr zone

Quote:> to the DNS server.

> If using "bind" I create names like...
> dhcp0-1.mydomain.com  (192.168.0.1)
> dhcp0-2.mydomain.com  (192.168.0.2)
> etc... In the above example, the in-addr zone name does not match the
actual FQDN of the
> client or NETBIOS name. But at least  the reverse lookup can be done. At
least until DDNS
> (Dynamic DNS) is released.

Is this a standard way of doing things?  It is a great suggestion, just
wondering how you came up with this solution....

Also, not that it is huge problem or concern, but would like to keep netbios
and dns names the same, if at all possible, or is it?

Is it possible to use even just the nmbd portion of Samba to help with the
cause?

Quote:> If using MS DNS server, I will configure the zones to use WINS for in-addr
lookups. That
> way when a MS client (or even Samba client) logins it will register with
the WINS server
> which in turn makes a entry in the appropriate DNS zone (when a DNS query
is received).
> This is a pretty cool feature of MS DNS. I have personally had a lot of
luck with this
> configuration but the key is setting up the proper TTL's to match the DHCP
scope
> expiration dates. Obviously, the linux box's resolver must also be

configured to use MS

- Show quoted text -

Quote:> DNS server. i.e. /etc/resolv.conf

> Steve Cowles

 
 
 

reverse name lookup & DHCP

Post by Steve Cowle » Sun, 28 Nov 1999 04:00:00







> > > How does one deal with reverse name lookup in a DHCP environment?

> > > Such as the problems with telnet etc. when their machines get their IP
> > > address via DHCP.

> > > A) they are not defined in DNS because their address changes...
> > > B) they are not defined in hosts/lmhosts etc because of the same
> reason...

> > > Would like some help with resolving this issue..

> > > TIA

> > > Keith

> > Even though DHCP clients addresses change, they must still be added to DNS
> zones. When I
> > setup DHCP servers and their associated scopes, I also add  the
> corresponding in-addr zone
> > to the DNS server.

> > If using "bind" I create names like...
> > dhcp0-1.mydomain.com  (192.168.0.1)
> > dhcp0-2.mydomain.com  (192.168.0.2)
> > etc... In the above example, the in-addr zone name does not match the
> actual FQDN of the
> > client or NETBIOS name. But at least  the reverse lookup can be done. At
> least until DDNS
> > (Dynamic DNS) is released.

> Is this a standard way of doing things?  It is a great suggestion, just
> wondering how you came up with this solution....

I don't know if I would go as far as to say my suggestion is a "standard". Given the fact
that NETBIOS and BIND are two totally separate "worlds"... the above works.

Quote:> Also, not that it is huge problem or concern, but would like to keep netbios
> and dns names the same, if at all possible, or is it?

This is easier said then done. It is possible to have a FQDN = NETBIOS name, but you would
have make sure that your DHCP server assigned the same IP to the client workstation every
time they connect to the network. Simply either increase the DHCP scope's lease time to
something like 2 months or reserve the IP addresses to a specific MAC address. Then
manually edit the DNS zones to correspond to the NETBIOS name of the client that is issued
the IP address. If you have a small enough network (like <25) this would not be to big of
an effort. Personally, I can think of better things to do with my time!  Plus what happens
if the user changes their NetBios name <groan>

Quote:

> Is it possible to use even just the nmbd portion of Samba to help with the
> cause?

Not sure what you mean, but if you are referring to using nmbd's WINS database to
create/update bind's zones then it might be possible. In fact, that's exactly what MS DNS
does. I would think that would be a pretty big project though. Again, I can think of
better things to do with my time than make bind and netbios "play" together. Besides, MS
W2K has eliminated WIN's (so to speak) and gone with DDNS and active directory.

Steve Cowles

- Show quoted text -

Quote:

> > If using MS DNS server, I will configure the zones to use WINS for in-addr
> lookups. That
> > way when a MS client (or even Samba client) logins it will register with
> the WINS server
> > which in turn makes a entry in the appropriate DNS zone (when a DNS query
> is received).
> > This is a pretty cool feature of MS DNS. I have personally had a lot of
> luck with this
> > configuration but the key is setting up the proper TTL's to match the DHCP
> scope
> > expiration dates. Obviously, the linux box's resolver must also be
> configured to use MS
> > DNS server. i.e. /etc/resolv.conf

> > Steve Cowles

 
 
 

reverse name lookup & DHCP

Post by eyeze » Mon, 29 Nov 1999 04:00:00



<major snippage applied>

Quote:> This is easier said then done. It is possible to have a FQDN = NETBIOS
name, but you would
> have make sure that your DHCP server assigned the same IP to the client
workstation every
> time they connect to the network. Simply either increase the DHCP scope's
lease time to
> something like 2 months or reserve the IP addresses to a specific MAC
address. Then
> manually edit the DNS zones to correspond to the NETBIOS name of the

client that is issued
Quote:> the IP address. If you have a small enough network (like <25) this would
not be to big of
> an effort. Personally, I can think of better things to do with my time!
Plus what happens
> if the user changes their NetBios name <groan>

The clients will be NT machines, so that will not be a problem.  I realize
that they are two different beast, however my main concern is less confusion
in the future(not mine somebody else's).  Mapping in dhcpd.conf seems like a
good way to go although it does kinda defeat the purpose doesn't it?  :-)
Well at least the network is initially <30 with a project growth of no more
than 50.
 
 
 

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I have started seeing error messages in my logs where the server seems
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Is there a way to keep the server from trying to get names for these
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