Your network contains an Active Directory domain named contoso.com. The network contains a member
server named Server1 that runs Windows Server 2012 R2. Server1 has the DNS Server server role installed
and has a primary zone for contoso.com.
The Active Directory domain contains 500 client computers. There are an additional 20 computers in aworkgroup.
You discover that every client computer on the network can add its record to the contoso.com zone.
You need to ensure that only the client computers in the Active Directory domain can register records in the
contoso.com zone.
What should you do first?
A.
Move the contoso.com zone to a domain controller that is configured as a DNS server.
B.
Configure the Dynamic updates settings of the contoso.com zone.
C.
Sign the contoso.com zone by using DNSSEC
D.
Configure the Security settings of the contoso.com zone.
Explanation:
If you install DNS server on a non-DC, then you are not able to create AD-integrated zones. DNS update
security is available only for zones that are integrated into AD DS. When your directory- integrate a zone,
access control list (ACL) editing features are available in DNS Manager so that you can add or remove users or
groups from the ACL for a specified zone or resource record.
1. Active Directory’s DNS Domain Name is NOT a single label name (“DOMAIN” vs. the minimal requirement of
”domain.com.” “domain.local”, etc.).
2. The Primary DNS Suffix MUST match the zone name that is allowing updates. Otherwise the client doesn’t
know what zone name to register in. You can also have a different Connection Specific Suffix in addition to the
Primary DNS Suffix to register into that zone as well.
3. AD/DNS zone MUST be configured to allow dynamic updates, whether Secure or Secure and Non-Secure.
For client machines, if a client is not joined to the domain, and the zone is set to Secure, it will not register
either.
4. You must ONLY use the DNS servers that host a copy of the AD zone name or have a reference to get to
them. Do not use your ISP’s, an external DNS address, your router as a DNS address, or any other DNS that
does not have a copy of the AD zone. Internet resolution for your machines will be accomplished by the Root
servers (Root Hints), however it’s recommended to configure a forwarder for efficient Internet resolution.
5. The domain controller is multihomed (which means it has more than one unteamed, active NIC, more than
one IP address, and/or RRAS is installed on the DC).
6. The DNS addresses configured in the client’s IP properties must ONLY reference the DNS server(s) hosting
the AD zone you want to update in. This means that you must NOT use an external DNS in any machine’s IP
property in an AD environment. You can’t mix them either. That’s because of the way the DNS Client side
resolver service works. Even if you mix up internal DNS and ISP’s DNS addresses, the resolver algorithm can
still have trouble asking the correct DNS server. It will ask the first one first. If it doesn’t get a response, it
removes the first one from the eligible resolvers list and goes to the next in the list. It will not go back to the first
one unless you restart the machine, restart the DNS Client service, or set a registry entry to cut the query TTL
to 0. The rule is to ONLY use your internal DNS server(s) and configure a forwarder to your ISP’s DNS for
efficient Internet resolution.
This is the reg entry to cut the query to 0 TTL:
The DNS Client service does not revert to using the first server. The Windows 2000 Domain Name System
(DNS) Client service (DNS cache) follows a certain algorithm when it decides the order in which to use the DNS
servers.
7. For DHCP clients, DHCP Option 006 for the clients are set to the same DNS server.
8. 8.If using DHCP, DHCP server must only be referencing the same exact DNS server(s) in its own IP
properties in order for it to ‘force’ (if you set that setting) registration into DNS. Otherwise, how would it know
which DNS to send the reg data to?
9. If the AD DNS Domain name is a single label name, such as “EXAMPLE”, and not the proper format of
”example.com” and/or any child of that format, such as “child1.example.com”, then we have a real big problem.
DNS will not allow registration into a single labeldomain name.
This is for two reasons:1. It’s not the proper hierarchal format. DNS is hierarchal, but a single label name has no hierarchy. It’s just
a single name.
2. Registration attempts cause major Internet queries to the Root servers. Why? Because it thinks the single
label name, such as “EXAMPLE”, is a TLD (Top Level Domain), such as “com”, “net”, etc. It will now try to
find what Root name server out there handles that TLD. In the end it comes back to itself and then attempts
to register. Unfortunately, it does NOT ask itself first for the mere reason it thinks it’s a TLD. (Quoted from
Alan Woods, Microsoft, 2004):
“Due to this excessive Root query traffic, which ISC found from a study that discovered Microsoft DNS
servers are causing excessive traffic because of single label names, Microsoft, being an internet friendly
neighbor and wanting to stop this problem for their neighbors, stopped the ability to register into DNS with
Windows 2000SP4, XP SP1, (especially XP, which cause lookup problems too), and Windows 2003. After
all, DNS is hierarchal, so therefore why even allow single label DNS domain names?” The above also
*especially* applies to Windows Vista, 7, 2008, 2008 R2, and newer.
10. ‘Register this connection’s address” on the client is not enabled under the NIC’s IP properties, DNS tab.
11. Maybe there’s a GPO set to force Secure updates and the machine isn’t a joined member of the domain.
12. ON 2000, 2003 and XP, the “DHCP client” Service not running. In 2008/Vista and newer, it’s the DNS Client
Service. This is a requirement for DNS registration and DNS resolution even if the client is not actually using
DHCP.
13. You can also configure DHCP to force register clients for you, as well as keep the DNS zone clean of old or
duplicate entries. Seethe link I posted in my previous post.