Internal and External namespace

Discussion in 'Windows Server' started by SeanL, Feb 22, 2006.

  1. SeanL

    SeanL Guest

    what would you say is the better way to configure your domains Active
    Directory -
    Should the namespace be the same as the external namespace example :
    mydomain.com
    or
    Should the internal namespace be seperate example : mydomain.local for
    internal and mydomain.com for external?
     
    SeanL, Feb 22, 2006
    #1
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  2. AD/DNS Namespace Planning - The Standard Three Options with
    Advantages/Disadvantages

    Can't decide on domain.com or domain.local for your AD domain? There are
    three differing views to this classic question and while they ultimately
    depend upon company preference, much of the direction will be driven by
    administrator experience. The three basic options outlined below are the
    most commonly-given answers to the question, and some companies use a
    combination of these scenarios. When explaining these to a relative
    beginner, many advanced AD/DNS administrators routinely their reasoning from
    their responses, but the explanations that follow contain detailed pros and
    cons of each.

    Option #1: Same internal and external DNS domain name.
    The administrator maintains entirely separate DNS implementations (no zone
    transfers, etc.), where the internal AD/DNS domain has manually configured
    static records (web, mail, etc..) to get to frequently used IP hosts in the
    public DNS zone of the same name (most likely provided by your ISP, unless
    you are a very large company). The private AD/DNS zone is protected inside
    the network perimeter and is used to support the internal AD. This is known
    as "shadow DNS", "split DNS", "split-brain" DNS, or "split-horizon" DNS.

    Advantages:
    1. Security: Each DNS zone is authoritative for the zone of that name so
    therefore the external DNS zone and internal AD/DNS zone will NOT replicate
    with each other thereby prevent internal company records to be visible to
    the outside Internet.
    2. Short namespace: Users don't have to type in (or see) a long domain name
    when accessing company resources either internally or externally. Names are
    "pretty".

    Disadvantages:
    1. Name resolution trap: If one is not careful, setting the internal AD
    domain to the same name as the external (public) DNS domain name will have
    the following consequences for internal AD users if their client machine's
    DNS settings are pointing to the external namespace DNS servers: Inability
    to access the public website, slow network logons, no group policy updates.
    2. Administrative overhead: Any changes made to the public DNS zone (such as
    the addition or removal of an important IP host such as a web server, mail
    server, or VPN server) must also be changed manually in the internal AD/DNS
    zone if internal users will be accessing these hosts from inside the network
    perimeter (a common circumstance).
    3. VPN resolution: Company users accessing the network from the Internet
    will easily be able to reach IP hosts in the public DNS zone but will not
    easily reach internal company resources inside the network perimeter without
    special (and manual) workarounds such as maintaining hosts files on their
    machines (which must be manually updated as well everytime there is a change
    to an important IP host in the public zone), or they must use special VPN
    software (usually expensive).

    For further reading on this scenario:

    http://www.isaserver.org/tutorials/You_Need_to_Create_a_Split_DNS.html
    http://homepages.tesco.net./~J.deBoynePollard/FGA/dns-split-horizon-common-server-names.html

    ---------------------------------------------------------------------------------------

    Option #2: Delegated subdomain.
    This is subdomain of the public DNS zone. For example,
    externaldnsdomain.com and subdomain.externaldnsname.com.

    Advantages:

    1. Security: Like Option #1, this method also isolates the internal company
    network (please note that this is also a disadvantage due to a longer DNS
    namespace (see note under 'Disadvantages' below).
    2. Administration: DNS records for the public DNS zone do not need to be
    manually duplicated into the internal AD/DNS zone.
    3. DNS resolution: Internal company (Active Directory) clients can resolve
    external resources in the public DNS zone easily, once proper DNS name
    resolution mechanisms such as forwarding, secondary zones, or delegation
    zones are set up.
    4. VPN resolution: VPN clients accessing the internal company network from
    the Internet can easily navigate into the internal subdomain. It is very
    reliable as long as the VPN stays connected.

    Disadvantages:

    First reported by Kevin G., MVP, he biggest technical problem I've seen if
    you choose a third level name of
    your public domain is if the hosting provider of your public domain's DNS
    uses a wildcard record in the public zone.
    Wildcard records play havoc on any name that is in the DNS suffix search
    list.
    By default the DNS client service appends the Primary DNS suffix and parent
    suffixes of the primary DNS suffix to all DNS queries not ending with a
    trailing dot. If your public DNS host doesn't use a wildcard there isn't a
    real issue. To check if your DNS hosing provider uses a wildcard query for
    *.domain.com (The asterisk is the wildcard)

    1. Longer DNS namespace: This may not look appealing (or "pretty") to the
    end-users.
    2. Security: While there is security in an isolated subdomain, there is a
    potential for exposure to outside attack, albeit extremely limited. The
    potential for exposure of internal company resources to the outside world,
    lies mainly in the fact that because when the public zone DNS servers
    receives a query for subdomain.externaldnsname.com, they will return the
    addresses of the internal DNS servers which will then provide answers to
    that query. Hackers could use this information to gather information about
    your network. To the extent, however, that internal networks are only
    accessible to the outside world via VPN (and/or exists within a non-Internet
    routable IP range) then this scenario is not a security disadvantage.

    The scenario is the recommendation from the Windows Server 2003 Deployment
    Guide. It states to the external registered name and take a sub zone from
    that as the DNS name for the Forest Root Domain

    http://www.microsoft.com/resources/documentation/windowsserv/2003/all/deployguide/en-us/default.asp

    ---------------------------------------------------------------------------------------

    Option #3: Different internal and external DNS domain names.

    For example, dnsname.com and dnsname.local. The administrator(s) maintain
    external records on the external DNS servers, and internal records on the
    internal DNS servers. For the internal domain, you can use any extension
    you want, such as .ad, int, .lan, etc...

    This option is usually best for beginners because it's the easiest to
    implement - primarily because it prevents name space conflicts from the very
    beginning with the public domain and requires no further action. But this
    option does make VPN resolution difficult (like Option #1) and, Exchange
    message headers will show the company internal AD name which looks
    unprofessional.

    Advantages:

    1. Easy setup. This method is the easiest to setup. DNS namespace
    collisions are avoided from the beginning. The internal AD domain will
    never conflict with any public domain.

    Disadvantages:

    1. Non-FQDN resolution. The chief disadvantage to this approach comes in
    when users have to access resources and don't use FQDNs. A Windows 2000/XP
    box where a user types "ping server1", for example, or types "server1" in
    IE, could potentially get unexpected results. For example, there is a
    machine named server1.internalname.com and there is also a server named
    server1.externalname.com. If a user opens Internet Explorer and simply types
    "server1" in the address bar (as often happens), then which "server1" is
    really the correct answer? The answer may notbe what the user was looking
    for, and it will be based off of the configuration settings of the
    following: DNS settings under the client's TCP/IP properties, the DNS
    suffix search order, WINS forwarding, domain membership, and whether or not
    it is using a proxy server.
    2. VPN resolution. VPN clients may encounter problems when trying to access
    internal resources. Newer VPN clients, such as those offered by Cisco and
    Nortel, once connected, provide name resolution by passing internal name
    servers (WINS, DNS) to the TCP/IP stack. If the VPN client cannot do this,
    add the host names of important internal hosts to the internal (WINS, DNS)
    name servers so that the VPN client will be able to resolve these names.
    Otherwise, you will need to use a Hosts (and Lmhosts if necessary) file,
    which is both manually intensive and will need to be updated whenever one of
    the listed IP host changes it's name or changes it's IP address, which
    happens often in an enterprise environment.

    For a broad overview of this entire topic, visit:

    DNS Namespace Planning
    http://support.microsoft.com/default.aspx?scid=kb;en-us;254680

    Assigning the Forest Root Domain Name
    http://www.microsoft.com/technet/pr...Kit/4bb9f469-df87-4830-96a8-b28ec71bafa9.mspx

    Conclusion:
    All three approaches will have to take both security and end-user experience
    into perspective. This perspective is colored by company size, budget, and
    experience of personnel running Active Directory and the network
    infrastructure (mostly with respect to DNS and VPN). No single approach
    should be considered the best solution under all circumstances. For any
    host name that you wish to be able to access from both your internal network
    and the Internet, you need Option #1, although it is the most
    administratively intensive over time. If you do not select this option and
    go with Option #2 or #3 only, then consideration will have to be given to
    the fact that company end-users will need to be trained on using different
    names under different circumstances based on where they are - at work, at
    home or on the road.
     
    Todd J Heron [MVP], Feb 23, 2006
    #2
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