Parses CAM table output from a Cisco switch, adding IP address, hostname, and OUI vendor info from a Windows DHCP server (2012 R2+)

Parse-CamTable.ps1

# Show all dynamic MACs, excluding the uplink trunk port
# Don't includer any header ouptput, only actual entries
# e.g., show mac address-table dynamic | ex Gi0/24
$ShMacAddrOutput = @"
   1    0023.ae57.3df2    DYNAMIC     Gi0/7
   1    0023.aeaf.77b2    DYNAMIC     Gi0/6
   1    14b3.1f01.00e4    DYNAMIC     Gi0/2
   1    28b2.bd8e.5459    DYNAMIC     Gi0/3
   1    28f1.0e32.a204    DYNAMIC     Gi0/1
   1    2c76.8ac4.f7e5    DYNAMIC     Gi0/3
   1    30cd.a73a.a0fe    DYNAMIC     Gi0/12
   1    4c57.ca63.0b5e    DYNAMIC     Gi0/3
   1    8843.e104.1246    DYNAMIC     Gi0/3
   1    a48d.3b56.b085    DYNAMIC     Gi0/3
   1    accc.8e49.b7a6    DYNAMIC     Gi0/18
   1    accc.8e49.b7ac    DYNAMIC     Gi0/16
   1    accc.8e49.b7c0    DYNAMIC     Gi0/17
   1    accc.8e55.b913    DYNAMIC     Gi0/15
   1    accc.8e5d.1ab1    DYNAMIC     Gi0/19
   1    accc.8e76.4716    DYNAMIC     Gi0/20
   1    b083.fe8f.86a3    DYNAMIC     Gi0/11
   1    b083.fe9b.5abc    DYNAMIC     Gi0/13
   1    b083.fe9b.5b47    DYNAMIC     Gi0/8
   1    e4a7.a04f.3689    DYNAMIC     Gi0/3
   1    f430.b92b.ffc0    DYNAMIC     Gi0/14
   1    f48e.38dd.6f63    DYNAMIC     Gi0/4
   5    0010.4948.856d    DYNAMIC     Gi0/13
   5    0010.4948.8576    DYNAMIC     Gi0/11
   5    0010.4948.85a3    DYNAMIC     Gi0/8
   5    0010.4949.2777    DYNAMIC     Gi0/2
   5    0010.4949.2780    DYNAMIC     Gi0/4
   5    0010.4949.d5ad    DYNAMIC     Gi0/22
   5    0010.4949.d5b1    DYNAMIC     Gi0/23
"@

# The command changed column layout. If you're on anything like
# modern gear, leave it on $new. If you have a very old IOS that uses
# show mac-address-table, change this to $old
$ShMacAddrCmd = $new

# show mac-address-table (old style)
$old = @('mac','type','vlan','port')
# show mac address-table (new style)
$new = @('vlan','mac','type','port')

# http://standards.ieee.org/develop/regauth/oui/oui.txt
# this file is huge or else I would pull it with Invoke-WebRequest
$OuiDb = 'oui.txt'

# Takes FastEthernet0/1 and returns Fa0/1
# Currently not used for anything
Function Truncate-PortName {
    Param ($FullPortName)
    $PortAbbreviation = $FullPortName.Substring(0,2)
    $PortID = $FullPortName -replace '[a-zA-Z]', ''
    return "${PortAbbreviation}${PortId}"
}

# Takes a MAC in the form of 0011.2233.4455
# Returns 00-11-22-33-44-55
Function Convert-DottedToDashedMac {
    Param ($MacAddress)
    $MacAddress = $MacAddress.Replace('.', '')
    $DashIndices = @(2,5,8,11,14)
    ForEach($Index in $DashIndices) {
        $MacAddress = $MacAddress.Insert($Index, '-')
    }
    Return $MacAddress
}

# Split on newline ('\r'), trim leading or trailing whitespace,
# then replace any run of one or more spaces with a comma.
# Finally, convert to an object array with ConvertFrom-Csv
$ParsedCamTable = ($ShMacAddrOutput -split '\r').trim() -replace '[ ]+', ',' | ConvertFrom-Csv -Header $ShMacAddrCmd

# Pull all DHCP scopes on the server
$Scopes = Get-DhcpServerv4Scope

# Resolve scope IDs (which are the subnet IDs) to VLANs
# Requires the scope have "VLAN X" in the description field,
# or else resolving DHCP IP addresses and hostnames will fail.
$ScopeList = @{}
$Scopes | % {
    If ($_.Description -like '*vlan*') {
        [int]$ScopeVlan = $_.Description -replace '[a-zA-Z]', ''
        $ScopeList[$ScopeVlan] += $_.ScopeId.IPAddressToString
    }
}

$output = @()
ForEach ($Entry in $ParsedCamTable) {
    # Convert MAC from 0011.2233.4455 to 00-11-22-33-44-55, as required for Get-DhcpServerv4Lease
    $mac = Convert-DottedToDashedMac $entry.mac

    # Obtain lease if we can. If not found, don't worry about it
    $Lease = Get-DhcpServerv4Lease -ClientId $mac -ScopeId $ScopeList[[int]$Entry.vlan] -ErrorAction SilentlyContinue

    # Yank OUI from MAC
    $Oui = $mac.substring(0,8)

    # Look up manufacturer from OUI database
    # This is pretty slow, probably some low-hanging fruit to optimize
    $Mfgr = ((Select-String $oui $ouidb | Select -exp line) -split '\t{2}')[1]

    # If we got lease info, add it to output. Otherwise leave blank.
    If ($Lease) {
        $IpAddress = $Lease.IPAddress.IPAddressToString
        $HostName = $Lease.HostName.split('.')[0]
    } Else {
        $IpAddress = ''
        $HostName = ''
    }
    
    # Append result object to output array
    $output += [PsCustomObject]@{
        Port = $Entry.port
        Mac = $entry.mac
        DhcpAddress = $IpAddress
        Vlan = $Entry.vlan
        DhcpHostName = $HostName
        Mfgr = $Mfgr
    }
}

# You can do whatever you want with $output which is an object array, but
# this construct is nice because it sorts output in a neat table,
# ordered by the numeric port value. If you just did $(sort -property Port),
# you'd get Gi0/2 and Gi0/20 next to each other, since it sorts as a [string]
# instead of an [int].
$Output | Sort-Object -Property {[int]($_.port -replace '[a-zA-Z/]', '')},Mac | Format-Table -AutoSize