Using Powershell, you can quickly verify the status of the replication between domain controllers in Active Directory. This can be used in monitoring to verify a healthy AD replication. This can be run on any domain controller or on another system with RSAT or ActiveDirectory Powershell module.
Get-ADReplicationPartnerMetadata -Target "$env:USERDNSDOMAIN" -Scope Domain | FT -Auto Server,LastReplication*
To see forest-wide replication, replace -Scope Domain with -Scope Forest.