So what’s going on behind the scenes in DHCP?

From the mail bag….


The SBS 2008 best practices state that the server itself should be the main DHCP server on the network. I’ve encountered situations that, for whatever reason, someone disabled the dhcp server on the server and enabled it on a gateway device or something else. In these cases, even if the workstation was assigned the server’s IP as the dns or if you set it statically, DNS resolution seems to not work as expected. There are certain resources that I cannot access. Mainly the “http://connect” site. To fix this issue, I always reconfigure those networks to have the sbs server as the main DHCP server, and I always perform my server installations in this way,  but I’ve always wondered why this happens.

I understand that that when a host leases an IP from the server. The server registers the IP and hostname in DNS, and that this doesn’t happen if the server does not assign an ip address.

But if the workstation is configured with the server’s IP as its dns server, shouldn’t the workstation be able to resolve
http://connect regardless if the workstation leased its IP from the server or not?


So why does finding the domain work when the server is handing out the DHCP, but not necessarily when the DHCP is on the router?



It’s all because of the DHCP scope options that are in there.


That’s the “why” and why we say having the Server hand out the DHCP is the best for SBS 2011 standard.


http://technet.microsoft.com/en-us/library/dd572752(office.13).aspx

2 Thoughts on “So what’s going on behind the scenes in DHCP?

  1. I had this issue on a site where the owner insisted on static IP addresses for a misguided security reason. Pinging “connect” would fail but pinging “connect.domain.local” would respond. Putting “connect.domain.local” into the address bar in IE would fail however, because the IIS connect site listens on “connect” and not the fqdn.

    Its the dns suffix that makes or breaks the deal. As long as the suffix is set manually or (if dhcp is in use) the 3rd party dhcp server can hand out the domain name, it should work fine.

  2. Keith,

    Can you explain DNS suffixs in more detail.

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