Tell me more ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.
up vote 0 down vote favorite

If I have a machine set up with DHCP, can I access it from inside a (corporate) network. I am assuming that the DNS servers will be able to resolve the hostname even across subnets. Am I correct? Can some one tell me what the usual norm (expected) behavior is?

For example, if I have a machine in a different country (in the same company) set up using DHCP, and I am told the dhcp name. Can I ping it?

share|improve this question
2  
Not enough info to assist. Please provide more info on the "problem" – Dave M Nov 3 '10 at 17:50
2  
It sounds to me like you would be doing yourself a great service by reading up on networking basics. – John Gardeniers Nov 3 '10 at 20:57
John, You are assuming things about me that you don't know. The question was specifically about if the DHCP hostbames are populated in the DNS Server or not. I KNOW networking and concepts but I do not know how the deployment is done in a corporate network. I cannot run with what I see in my home network and so I was trying to tap into the community's knowledge. – user59048 Nov 4 '10 at 2:32

3 Answers

up vote 0 down vote accepted

There are three things here:

1. Does the DHCP server hand out IP addresses that are configured in DNS?

It may, and it may not. The DHCP server on my home network, for example, gives out addresses which it also provides DNS answers for. At work, the DHCP server and DNS servers are completely separate, but the DNS server is populated from a database that knows about the systems registered to use DHCP.

2. Are the DNS addresses given out to your system "real" public DNS records?

In my case at home, no, they're not -- they're invalid .local addresses. They work because my internal systems are resolving addresses using my DHCP/DNS box, which has been configured to answer queries from my internal network. Even if I opened that box up to the world, no one else would know to look at it to get an answer for "laptop.local", because the root servers don't know about it.

3. And finally, are the IP addresses given out public addresses rather than 10.x.x.x or 192.168.x.x (or other) private-range addresses? And, (point 3½) if they are public, is there a network firewall which protects the system from external access?

In the example of my home network, they're private addresses. At work, we're migrating to private addresses, but some systems are given NAT access through the firewall. (This isn't the default and needs to be justified and configured on a per-system basis.)

share|improve this answer
Thank you for answering my question. Though the question could have been framed better you understood it. I wanted to know how the corporate deployment works and know that what I see at home is not correct. – user59048 Nov 4 '10 at 2:33
up vote 0 down vote

There's a lot of misconceptions in this question about how things work -- you don't need DNS for DHCP to work, and DNS has nothing to do with the subnet/routing configuration in your network. What's the actual problem that you're trying to solve?

share|improve this answer
Agreed... You can ping it if you can resolve it by name AND the IP is routable. There is no expected norm. here as you ask. It's entirely up to the design. I would say that you shouldn't be able to ping other hosts in the same company if there isn't a legitimate need. If the two hosts are in different departments or divisions you may not need them to talk to each other and thus that traffic might be firewalled or segregated by other means. – Aaron Copley Nov 3 '10 at 17:50
2  
You aren't actually answering the question, so this should be a comment on the question rather than an answer. – ThatGraemeGuy Nov 3 '10 at 20:47
You are assumiong things about me that you don't know. The question was specifically about if the DHCP hostbames are populated in the DNS Server or not. I KNOW networking and concepts but I do not know how the deployment is done in a corporate network. I cannot run with what I see in my home network and so I was trying to tap into the community's knowledge. – user59048 Nov 4 '10 at 2:30
Aaron, I think you nailed it. That was what I was looking for. DHCP hostnames even if the IP addresses are private must be reachable since they will be NAT'ed. But I cannot expect IP addresses across subnets be reachable and they most likely won't be. – user59048 Nov 4 '10 at 3:58
up vote 0 down vote

The quick answer in a corporate environment is No. DHCP is used for hosts which are expected to be clients not servers. DHCP addresses are not usually listed in DNS. Servers are given static addresses and appropriate DNS names.

The long answer is maybe. The corporate DNS servers may be configured to allow DHCP clients to register their address. If so, and if the client actually registers its name it should be reachable by name.

DHCP is now mostly used for the private DNS ranges 10.0.0.0/8 192.168.0.0/16 and 172.16.0.0/12. These are not reachable across the Internet. Unless your corporate network includes the remote site, it is unlikely be reachable.

share|improve this answer
We use static (same address every time) DHCP for servers. This speeds up system deployment, prevents accidental conflicts, and helps us manage the environment better. And on the other hand, we definitely provide DNS addresses for clients as well. This isn't done on a client-push basis, but is instead centrally controlled. – mattdm Nov 3 '10 at 20:25
Thank you for answering my question without questioning my knowledge of networking. Though the question could have been framed better you understood it. I wanted to know how the corporate deployment works and know that what I see at home is not correct. – user59048 Nov 4 '10 at 2:32
Even DHCP is mostly used with private IP Addresses they will be NAT'ed which means that NAT server will atleast be in the DNS server locally. Which means the hostname will be reachable within the company. Correct? – user59048 Nov 4 '10 at 3:56
@user59048 NAT will not help within the local network The host's name is often not registered in DNS and therefore the host is not reachable by name. Large corporations will usually have multiple LANs, MANs and/or WANs. These will likely have limited connectivity between them. This could render a host unreachable from many parts of the corporate network. – BillThor Nov 5 '10 at 3:22
@mattdm Serves using DHCP should have static leases (IP addresses) and DNS entries. DHCP in this case is just another way to assign the server its static address. However, using DHCP breaks down when a server needs multiple addresses. – BillThor Nov 5 '10 at 3:32
show 1 more comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.