Posts Tagged ‘DNS’

Record type

Name

Description

A Address Record Maps a hostname to an IP address
PTR Pointer Record Maps an IP address to a hostname
CNAME Alias Record Maps an alias to a hostname
MX Mail Exchanger Record Specifies a mail route for a domain
NS Name Server Record Specifies name servers for a given domain
SOA Start of Authority Record Contains administrative data about a zone, including the primary name server
SRV Service Record Maps a particular service (e.g., LDAP) to one or more hostnames

One important resource record to note is the SRV record type. SRV records are used extensively by domain controllers and Active Directory clients to locate servers that have a particular service.

 

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Symptoms:

–          The Server service fails to start and the below events are recorded

Event ID: 7023

Source: Service Control manager

Type: Error

Description: The Server service terminated with the following error: More data is available.

–          Not Enough storage is available to process this command.

Event ID: 7001

Source: Service Control manager

Type: Error

Description: The Netlogon service depends on the server service which failed to start because of the following error: More data is available.

–          System Error 8 has occurred. Not enough storage is available to process this command.

–          If you try to start the Server Service manually, the following errors may occur: A System error has occurred: System Error 234 has occurred.

–          You will not be able to execute any command in the Server.

–          You get error message when you open the Network connections (ncpa.cpl)

Observations:

–          Other services may fail to start because these services are dependent on the Server Service.

–          The Server service queries the registry value above for its entries. The buffer for the amount of information that the Server service can accept when it queries is approximately 32 KB. If there are more than 32 KB in that entry, the Server service will fail to start and return the error “More data is available,” or “Not enough storage is available.”

–          It looks like certain software’s can also cause for this error, those maybe the Norton Antivirus, Acronis trueImage, Seagate DiscWizard, IBM antivirus, Microsoft Bitdefender, Symantec Endpoint Protection or AVG, Try Disabling them or uninstalling and check if the problem persists.

–          You can instantly rectify this error if you restart the server, but the error re-occurs in 2 to 3 days.

Resolution:

PLEASE BACKUP YOUR REGISTRY FIRST BEFORE YOU MAKE ANY CHANGES

This issue may be cause of two reasons, one is the NullSessionPipes and the other is IRPStackSize.

  1. NullSessionPipes

The Cause of these errors is due to too much data stored in the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters\NullSessionPipes

The Server service queries the registry value above for its entries. The buffer for the amount of information that the Server service can accept when it queries is approximately 32 KB. If there are more than 32 KB in that entry, the Server service will fail to start and return the error “More data is available,” or “Not enough storage is available.”

The Solution is to remove any unnecessary entries from this value in the registry.

The Default information stored in this key is:

COMNAP

COMNODE

SQL\QUERY

SPOOLSS

LLSRPC

EPMAPPER

LOCATOR

  1. IRPStackSize

Go to the below Registry entry to edit the IRPStackSize

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters

If you do not have the Registry entry then create one manually, but make sure the name should be correct as it is case sensitive.

To create the Registry entry follow the below steps:

–          Open REGEDIT

–          Proceed to the following location: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters

–          Click Edit, and point to New and then click DWORD Value

–          Type IRPStackSize , Click Edit and then modify the Value

–          The Value should be 0x00000050 in Hexadecimal or 80 in Decimal. This should resolve your issue, normally values are provided to 1 to 15 in decimal notation. Better if you provide higher value so that the problem doesn’t come back.

–          Restart the Server after the changes are done.

Introduction

Replication ensures that all information in Active Directory is current on all domain controllers and client computers across your entire network. Many networks consist of a number of smaller networks, and the network links between these networks may operate at varying speeds. Sites in Active Directory enable you to control replication traffic and other types of traffic related to Active Directory across these various network links. You can use subnet objects, site links, and site link bridges to help control the replication topology when configuring replication between sites. An efficient, reliable replication topology depends on the configuration of site links and site link bridges.

 

What Are Sites and Subnet Objects?

 

Introduction

You use sites to control replication traffic, logon traffic, and requests to the Global Catalog server.

 

Sites

In Active Directory, sites help define the physical structure of a network. A site is defined by a set of Transmission Control Protocol/Internet Protocol (TCP/IP) subnet address ranges. Sites are used to define a group of domain controllers that are well-connected in terms of speed and cost. Sites consist of server objects, which contain connection objects that enable replication.

 

Subnet Objects

The TCP/IP subnet address ranges are represented by subnet objects that group computers. For example, a subnet object might represent all the computers on a floor in a building, or on a campus. Subnet objects are associated with sites and, because the subnet objects map to the physical network, so do the sites. For example, if you have three subnets that represent three campuses in a city, and these campuses are connected by high-speed, highly available connections, you could associate each of those subnets with the same site. A site can consist of one or more subnets. For example, on a network with three subnets in London and two in Boston, the administrator can create a site in London, a site in Boston, and then add the subnets to the respective sites.

 

Default Site

A default site is set up automatically when you install Windows Server on the first domain controller in a forest. This site is called Default-First-Site- Name. This site can be renamed. When you create your first domain in a forest it is automatically placed in the default site.

Introduction

A global catalog server is a domain controller that stores two forest-wide partitions, schema and configuration, a read/write copy of the partition from its own domain, and also a partial replica of all other domain partitions in the forest. These partial replicas contain a read-only subset of the information in each domain partition.

 

How does replication affect the global catalog server?

When a new domain is added to a forest, the information about the new domain is stored in the configuration partition, which is replicated to all domain controllers, including global catalog servers, through normal forest-wide replication. Then each global catalog server becomes a partial replica of the new domain by contacting a domain controller for that domain and obtaining the partial replica information. The configuration partition also contains a list of all global catalog servers in the forest and provides this information to the domain controllers. Global catalog servers register special DNS records in the DNS zone that correspond to the Forest Root domain. These records, which are registered only in the Forest Root DNS zone, help clients and servers locate global catalog servers throughout the forest.

Introduction

When you add domain controllers to a site, Active Directory uses the Knowledge Consistency Checker (KCC) to establish a replication path between domain controllers.

 

What is Knowledge Consistency Checker?

The KCC is a built-in process that runs on each domain controller and generates the replication topology for all directory partitions contained on that domain controller. The KCC runs at specified intervals (every 15 minutes by default) and designates replication routes between domain controllers that are the most favorable connections available at the time.

 

How KCC works?

To automatically generate a replication topology, the KCC evaluates information in the configuration partition on sites, the cost of sending data between these sites, any existing connection objects, and the replication protocols that can be used between the sites. Next, the KCC calculates the best connections for a domain controller’s directory partitions to other domain controllers. Additionally, if replication within a site becomes impossible or has a single point of failure, the KCC automatically establishes new connection objects between domain controllers to maintain Active Directory replication.

Partitions:-

Introductions

The Active Directory database is logically separated into directory partitions, a schema partition, a configuration partition, domain partitions, and application partitions. Each partition is a unit of replication, and each partition has its own replication topology. Replication is performed between directory partition replicas. All domain controllers in the same forest have at least two directory partitions in common: the schema and configuration partitions. All domain controllers in the same domain, in addition, share a common domain partition.

 

Schema Partition:

There is only one schema partition per forest. The schema partition is stored on all domain controllers in a forest. The schema partition contains definitions of all objects and attributes that can be created in the directory, and the rules for creating and manipulating them. Schema information is replicated to all domain controllers in the forest, so all objects must comply with the schema object and attribute definitions.

 

Configuration Partition:

There is only one configuration partition per forest. The configuration partition is stored on all domain controllers in a forest. The configuration partition contains information about the forest-wide Active Directory structure, including what domains and sites exist, which domain controllers exist in each, and which services are available. Configuration information is replicated to all domain controllers in a forest.

 

Domain Partition:

There can be many domain partitions per forest. The domain partitions are stored on all of the domain controllers of the given domain. A domain partition holds information about all domain-specific objects created in that domain, including users, groups, computers, and organizational units. The domain partition is replicated to all domain controllers of that domain. All objects in every domain partition in a forest are stored in the Global Catalog with only a subset of its attribute values.

 

REPLICATIONS:

The replication process occurs between two domain controllers at a time. Over time, replication synchronizes information in Active Directory for an entire forest of domain controllers. To create a replication topology, Active Directory must determine which domain controllers replicate data with other domain controllers.

 

This is how the name resolution works:

  1. You try to open up a Webpage on the Ignited Soul website, to do so, you type http://Ignitedsoul.com in the address bar of your browser and then press Enter, That’s when the Name Resolution begins.
  2. Your Computer sends out a request to its local DNS server or at least to one of the servers listed in its IP configuration settings for the same.
  3. If this server doesn’t include the name in its own database or cache, it sends a referral request to the name server. Because the Ignitedsoul site name ends in .com, the DNS server sends the referral to the .com name server.
  4. The .com name server is the authority for all names that end in the .com suffix. This server knows the location of all DNS servers that are the final authorities for a particular name ending with .com. in this case; it sends the request to the authoritative DNS server for the ignitedsoul.com name.
  5. The DNS server for ignitedsoul.com sends the corresponding IP address for the requested page to the client computer.
  6. The name resolver on the client uses the IP address to request the actual page from its internet provider.
  7. If the page is not already in the local cache of the internet provider, it requests the actual page and sends it to the client.

This DNS Name resolution process occurs within seconds, and the website appears almost as fast as you type it in browser, also depending on the speed of your Internet connection and the current load of the requested server. That’s what happens when you look at the green progress bar at the bottom of your browser. The actual progress also includes downloading the content such as the text and the graphics to your own computer.

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and routing Internet Protocol packets. It is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes. As a result, the number of available Internet addresses has been greatly increased. CIDR is now the routing system used by virtually all gateway hosts on the Internet’s backbone network.

IP addresses are described as consisting of two groups of bits in the address: the more significant part is the network address, which identifies a whole network or subnet, and the less significant portion is the host identifier, which specifies a particular interface of a host on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies. Classful network design for IPv4 sized the network address as one or more 8-bit groups, resulting in the blocks of Class A, B, or C addresses. Classless Inter-Domain Routing allocates address space to Internet service providers and end users on any address bit boundary, instead of on 8-bit segments. In IPv6, however, the interface identifier has a fixed size of 64 bits by convention, and smaller subnets are never allocated to end users.

CIDR notation is a syntax of specifying IP addresses and their associated routing prefix. It appends to the address a slash character and the decimal number of leading bits of the routing prefix, e.g., 192.0.2.0/24 for IPv4, and 2001:db8::/32 for IPv6.

If a DNS Server does not have an entry in its database for the remote host specified in a client request, it can respond to the client with the address of a DNS Server more likely to have that information, or it can query the other DNS server itself. This process can take place recursively until either the client computer receives the IP address or the DNS server establishes that the queried name cannot be resolved. DNS Servers to which other DNS Servers forward requests are known as Forwarders.

The Windows 2008 DNS Server service extends the standard forwarder configuration by using conditional forwarders. A Conditional Forwarder is a DNS Server that forwards DNS Query according to the DNS domain name in the query. For example, you can configure a DNS server to forward all the queries that it receives for names ending with Ignitedsoul.com to the IP address of one or more specified DNS Servers. This feature is particularly useful on extranets, where several organizations and domains access the same private internetwork.

Other Posts Related to DNS:

https://ignitedsoul.com/2012/01/25/dns-record-keeping/

 

DNS keeps track of Information in Zones. Essentially, a zone is a flat-file database for a particular domain, such as http://www.Google.com. The zone can contain different rexord types, all of which can be queried by clients:

> A : Which i a Host Address record – this resolves a single host name. suck as www, to an IP address.

> CNAME : or Alias – This resolves a name such as www to an actual host name, such as www1. think of it as a nickname for a computer -“www”, for example, is easier to remember and more standardized than a computer name like “w4salwin” which is what a Web Server’s real name might be.

> MX : or Mail Exchanger – This provides the name of the mail server for a Domain. Multiple MX records can be provided for fault tolerance or load balancing and a prioroty assigned to each. Clients, Such as sending mail servers, will attempt to contact the server in the MX record with the lowest-Numbered Priority.

> AAAA – This maps an IPv6 IP address to a host name.

> SRV: or Service – This provides the IP address of  one or more servers providing a particular service. AD uses SRV records to allow clients to locate Domain Controllers, among other things.

> SOA: or Start of Authority – This Special record indicates that the DNS Server hosting the zone is authoritative for the zone and is the primary source of name resolution for hosts within that domain.