DHCP/DNS server

[rsenio]

OK bear with me while I try to explain my problem. I'm somewhat a Linux noob, so this maybe an easy solution for you.

LaptopA is on it's own subnet, it's handed an address by a linux DHCP server. It can ping anything on side A or side B (separate sublent) by name and IP. DHCP server cannot ping laptopA by name only by IP, but can ping sideB by either. SideB cannot ping sideA by name, only by IP. The problem lies somewhere in the config of my DHCP linux server I think. But all the parameters that it's handing out are correct.

When I do an nslookup from the linux dhcp server I can see that it's looking at the correct DNS server but it comes back SERVFAIL. Yet, when I do an nslookup for something on sideB it comes back with correct results.

I know this may sound really confusing, but I NEED help!!! if you need any other information or clarification please ask. I will watch this post. Your my last hope! Thanks in advance

 

[thedaver]

You could post your DHCP conf files... but,
DHCP doesn't tend to make hostname entries in "DNS" services, unlike WINS.

What you described is what I'd expect - pinging by IPs works by name doesn't.

?

D.E.R. Management - IT Project Management Consulting

http://www.dermanagement.com/

 

[rsenio]

That is correct. Client A which gets it's DHCP from the lunix box can ping anything on either side by IP or hostname. THe linux server can only ping clientA by ip, yet it can ping side b by either name or IP. Clients on side B cannot ping by name side A, only the linux box. So what entry am I missing to make this all work?

 

[thedaver]

OK, first, your question is ambiguous. Getting "it" to work isn't sufficient...

However, let's take a look at what's what.

If a given IP can ping another IP on your network, then that's a statement of goodness.

DHCP does NOT create name references for dynamically assigned IPs as part of its default functionality. In fact, I don't believe it would at all. You're thinking of the WINS service under Windows, but that doesn't apply here.

Your name-based (DNS) resolution is obviously working because you set it up to work.

Think about it, if your ClientA is a moving target because of IP reassignment through DHCP lease expiration, you should not have an expectation that it would resolve reliably by name.

There are services that can assist with public IPs on dynamically assigned DHCP leases, but that's probably not what you're working with here. I'm assuming that you've got a local network and you're frustrated that DHCP isn't providing name-based resolution of the DHCP fed clients.

correct or not?

D.E.R. Management - IT Project Management Consulting

http://www.dermanagement.com/

 

[rsenio]

I realize the DHCP has nothing to do with name resolution. The whole network is 2k3 actually. Except for this one segment. The linux box has the proper DNS server set, as well as handing out the DNS information to the clients as part of DHCP. Which is why the client getting it's address from the linux box is able to ping anything by name. What I need to figure out to get everything working is why I can't do a nslookup for one of it's own DHCP clients. It fails. Yet I can do it for other PC's on a different segment. I appreciate your assistance. Perhaps when I get back to the office tomorrow I can post a more detailed map of the network. Too bad I can't post pictures.

 

[QatQat]

Just speculating now, if you have a windoz domain server on a windoz network, chanches are that your windoz server is handling name resolution and your linux box is probably a slave DNS server.
You therefore may look for solutions on the windoz 2003 server or, speculating again, you may be experiencing some routing problems in between the two subnets (i.e. one subnet cannot reach the windoz server to resolve DNS queries).

WHich one is your primary name server? Is linux routing between the two subnets?

QatQat




Life is what happens when you are making other plans.

 

[thedaver]

What I need to figure out to get everything working is why I can't do a nslookup for one of it's own DHCP clients.

For the third, and last time, friend, DHCP does NOT alter anything that supports lookups by name! Windows WINS does that, DHCP on linux does NOT.

Therefore, your Windows segment users will see different name resolution services/results than those served as DHCP on the linux segment.

If you have DNS running on linux for STATIC assigned name/IP pairs that is not working, then we can talk further. Otherwise, my estimation is that you're trying to get Windows functionality to work where it can't/won't.

D.E.R. Management - IT Project Management Consulting

http://www.dermanagement.com/

 

[QatQat]

Hi thedaver,

I also have a feeling the two things are getting mixed up here.
I still suspect that a windoz server is doing the name resolution (probably just because is setup as domain controller that usually takes on the DNS job too);

rsenio,
the sentence below

I realize the DHCP has nothing to do with name resolution

is in contrast with

The linux box has the proper DNS server set, as well as handing out the DNS information to the clients as part of DHCP

WHat the DHCP server will do is to tell you which machine acts as a DNS resolver.
What DHCP will not do is resolve DNS queries.
If in the set of information sent out to clients is also the linux machine's address as DNS server, then, I repeat, one of the two servers has to query information from the other and the two subnets have to be routed together somehow; guessing, I would let linux do the job as windoz as a router is close to ridiculous.

Cheers

QatQat


Life is what happens when you are making other plans.

 

[rsenio]

Yes, a 2k3 box on the other side handles DNS. Clients are gathering that information as part of the DHCP settings the linux box is handing out. The clients can do ping by names. Yet, for some reason they are not letting the 2k3box know where they are. There for from the other side, I cannot ping them by name.

The linux box, as part of it's network setup also has the 2k3box set as it's DNS server. Yet it cannot ping clients on it's side by name either, yet it can ping clients on the other side by name. I'll post some more info. Along with the dhcpd.conf contents

 

[rsenio]

And, the nslookup is going to the DNS server to get results. It fails, obviously. The clients are not reporting to the DNS server. Yet they are able to query it when they ping by name. Odd eh.

 

[thedaver]

Yes, a 2k3 box on the other side handles DNS"

OK, ALL DNS?!

"Clients are gathering that information as part of the DHCP settings the linux box is handing out."

OK, so DHCP is telling clients to use the windows box to resolve names... all names. The linux box itself is routing and providing IPs by DHCP ONLY!

"The clients can do ping by names."

OK, that means they can see the Win2K3 DNS server and are able to resolve names for what the DNS server "knows about".

"Yet, for some reason they are not letting the 2k3box know where they are."

THAT'S WHAT I'VE BEEN TRYING TO TELL YOU!!!!!!!
Linux DHCP does NOT provide the WINS instructions for the clients to register themselves into the Win2K3 DNS services as dynamically assigned clients.

"The linux box, as part of it's network setup also has the 2k3box set as it's DNS server. Yet it cannot ping clients on it's side by name either, yet it can ping clients on the other side by name."

Not surprising at all. The linux machine and its side of clients are playing by the rules. The Win2K3 machine only knows about the names of the WINS participants. The linux side's clients are NOT WINS participants since they get DHCP from linux.

I'm done with this thread now.











D.E.R. Management - IT Project Management Consulting

http://www.dermanagement.com/

 

[rsenio]

Client A (DHCP info)
IP: 192.168.126.xxx
Gateway:192.168.126.254
DNS server: 192.168.26.6
Subnet:255.255.255.0

Linux DHCP Server
IP:192.168.126.6
Gateway:192.168.126.254
DNS server: 192.168.26.6
Subnet :255.255.255.0

Client B (DHCP info)
IP:192.168.26.xxx
Gateway:192.168.26.2
DNS Server:192.168.26.6
Subnet:255.255.0.0

DNS Server/DHCP Server 2K3
IP:192.168.26.6

 

[rsenio]

Wow thedaver, I suppose I can say that was helpful. I'll leave it at that though. Now that you have reiterated my problem the reason I posted here was for a solution.

Here is the contents of the dhcpd.conf

# DHCP Server Configuration file.
# see /usr/share/doc/dhcp*/dhcpd.conf.sample
#
ddns-update-style interim;
ignore client-updates;

subnet 192.168.126.0 netmask 255.255.255.0 {

# --- default gateway
option routers 192.168.126.254;
option subnet-mask 255.255.255.0;

option nis-domain "XXXX.com";
option domain-name "XXXX.com";
option domain-name-servers 192.168.26.6, 192.168.26.1;
option netbios-name-servers 192.168.26.6, 192.168.26.1;
option netbios-node-type 8; ### Node type = Hybrid ###
ddns-updates on; ### Dynamic DNS enabled ###

option time-offset -18120; # MST Standard Time
option ntp-servers 192.168.26.197;
option tftp-server-name "192.168.26.197";
# dhcp-option66 192.168.26.197;

range dynamic-bootp 192.168.126.08 192.168.126.149;
default-lease-time 432000;
max-lease-time 432000;

# we want the nameserver to appear at a fixed address
#host jetdirect
#{
#hardware ethernet 00:0E:7F:E9:71:33;
#fixed-address 192.168.126.208;
#}
}

 

[Annihilannic]

rsenio,

What thedaver and most people who have replied have been saying is that you are expecting functionality that simply doesn't exist without adding additional software, or writing your own, to add DHCP clients of the Linux box to DNS.

When a DHCP client connects it simply says "I'd like an IP address please and the name of my DNS server, etc.". It doesn't say, "Hi, my name is funkyjim and I'd like an IP address and the name of my DNS server, oh, and can you please register me in DNS too."

Someone else asking a similar question and getting a similar answer:

http://help.lockergnome.com/windows2/Dynamic-Linux-DHCP-ftopict472998.html

This article mentions that Linux DHCP can register clients in DNS, but they will get dynamically generated names:

http://www.iqware.co.uk/dhcp-3.php

This might be interesting (and any other results you can find by Googling for "dhcp dynamic dns"):

http://www.mattfoster.clara.co.uk/ddns.htm

Annihilannic.

 

[rsenio]

Well I'm not sure what entry I added/edited yesterday. But it is working. Now, when I renew the DHCP assignment on clientA I am able to ping them by name on a client sitting at another site. Thanks to everyone.