Builds a topology for use with cardano-node. Set your own block producing relays inside the $newRelays object. Only looks for relays with addresses like *relays* but you can easily customise it. Creates a file called mainnet-topology.json

Cardano-topology-builder.ps1

$relays = Invoke-WebRequest -Uri https://explorer.mainnet.cardano.org/relays/topology.json | ConvertFrom-Json

$relays2 = $relays.Producers | Where-Object {
    $_.addr -like '*relays*'
} | Sort-Object { $_.addr -eq 'relays-new.cardano-mainnet.iohk.io' } -Descending

$newRelays = @{
    "Producers" = [Collections.ArrayList]@(
        @{
            "addr" = "127.0.0.1"
            "port" = 8000
            "valency" = 1
        }
    )
}

foreach ($relay in $relays2) {
    $valency = (Resolve-DnsName $relay.addr).Count

    $newRelays.Producers.Add(
        @{
            "addr" = $relay.addr
            "port" = $relay.port
            "valency" = $valency
        }
    ) | Out-Null
}

$newRelays | ConvertTo-Json | Out-File mainnet-topology.json