Finding Duplicate IP Addresses and Duplicate Names in a DNS Zone

One of the traditional issues associated with cleaning up an Active Directory Directory Services (AD DS) domain in DNS is to ensure that duplicate names in DNS are removed (this is typically an issue caused by not having DNS Scavenging enabled, or by having hosts forcefully removed from the domain and not properly cleaning up DNS). As a corollary, this can also lead to duplication of manually assigned IP addresses, regardless of whether those IP addresses are IPv4 or IPv6.

Duplications can cause issues for many different servers and services, including AD DS, Exchange, SharePoint, etc.

I've written a PowerShell script that can help you determine the duplicates in order to clean those up. See the script below!

## ## build-dns-objects.ps1 ## ## ## Michael B. Smith ## michael (at) TheEssentialExchange.com ## April, 2012 ## ## ## Primary functionality: ## ## Based on either an input file or the output of a default command: ## ## dnscmd ( $env:LogonServer ).SubString( 2 ) /enumrecords $env:UserDnsDomain "@" ## ## Create an array containing all of the DNS objects describing the input. ## ## ---- ## ## Secondary functionality: ## ## Find all the duplicate IP addresses and the duplicate names ## contained within either the file or the command output. ## ## By specifying the -skipRoot option, all records for the root of ## the domain are ignored. ## ## ## General record format returned by DNScmd.exe: ## ## name ## [aging:xxxxxxxx] ## TTL ## resource-record-type ## value ## [optional additional values] ## ## Fields may be separated by one-or-more spaces or one-or-more tabs ## [aging:xxxxxxxx] fields are optional ## Param( [string]$filename, [switch]$skipRoot ) function new-dns-object { return ( "" | Select Name, Aging, TTL, RRtype, Value ) } function tmpFileName { [string] $strFile = ( Join-Path $Env:Temp ( Get-Random ) ) + ".txt" if( ( Test-Path -Path $strFile -PathType Leaf ) ) { rm $strNetworkFile -EA 0 if( $? ) { ## write-output "...file was deleted" } else { ## write-output "...couldn't delete file, error: $($error[0].ToString())" } } return $strFile } if( $filename -and ( $filename.Length -gt 0 ) ) { $tmp = $filename } else { $tmp = tmpFileName dnscmd ( $env:LogonServer ).SubString( 2 ) /enumrecords $env:UserDnsDomain "@" >$tmp } $objects = @() $records = gc $tmp $script:zone = '' ## Primary functionality: foreach( $record in $records ) { ## write-output "Processing: $record" if( !$record ) { continue } if( $record -eq "Returned records:" ) { continue } if( $record -eq "Command completed successfully." ) { continue } $firstChar = $record.SubString( 0, 1 ) $record = $record.Trim() if( $record.Length -eq 0 ) { continue } $object = new-dns-object $index = 0 $record = $record.Replace( "`t", " " ) $array = $record.Split( ' ' ) if( ( $firstchar -eq " " ) -or ( $firstchar -eq "`t" ) ) { $object.Name = $script:Zone } else { $object.Name = $array[ 0 ] $script:Zone = $array[ 0 ] $index++ } if( ( $array[ $index ].Length –ge 3 ) –and ( $array[ $index ].SubString( 0, 3 ) –eq “[Ag” ) ) ## [Aging:3604987] { $object.Aging = $array[ $index ] $index++ } $object.TTL = $array[ $index ] $object.RRType = $array[ $index + 1 ] $object.Value = $array[ $index + 2 ] $objects += $object } ## Secondary functionality: ## There are more efficient ways to do this, but this is easy. ## search for duplicate names $hash = @{} foreach( $o in $objects ) { if( $o.RRtype -eq "A" ) { $name = $o.Name if( $skipRoot -and ( $name -eq "@" ) ) { continue } if( $hash.$name ) { "Duplicate name: $name, IP: $($o.Value), original IP: $($hash.$name)" } else { $hash.$name = $o.Value } } } $hash = $null ## search for duplicate IP addresses $hash = @{} foreach( $o in $objects ) { if( $o.RRtype -eq "A" ) { if( $skipRoot -and ( $o.Name -eq "@" ) ) { continue } $ip = $o.Value if( $hash.$ip ) { "Duplicate IP: $ip, name: $($o.Name), original name: $($hash.$ip)" } else { $hash.$ip = $o.Name } } } $hash = $null " " "Done"
Published Tuesday, April 24, 2012 1:53 PM by michael

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