Sites, Subnets ו־Replication

A Site represents a physical location with good network connectivity. uses Sites so the client connects to the nearest DC, and to schedule efficient Replication between sites.

Intra-site Replication — fast, nearly instant, no compression.
Inter-site Replication — scheduled (default every 180 minutes), with compression.
A Subnet must be associated with a Site, otherwise clients will connect to a random DC.

repadmin /replsummary
repadmin /showrepl
Get-ADReplicationSubnet -Filter *
nltest /dsgetsite

powershell

Domain controllers replicate quickly and without compression inside a site. Between sites, compressed data follows a site-link schedule. Subnet mapping sends clients to the closest controller.

Architecture and Theory — Under the Hood

Sites reflect the physical topology (branches) of the network. KCC automatically builds replication links within a Site (every 15 seconds, uncompressed) and between Sites (according to schedule, compressed).

Practical Configuration (PowerShell / GUI)

# Create Site and link Subnet
New-ADReplicationSite -Name "TLV"
New-ADReplicationSubnet -Name "10.20.0.0/16" -Site "TLV"

# Link between Sites
New-ADReplicationSiteLink -Name "HQ-TLV" -SitesIncluded HQ,TLV -Cost 100 -ReplicationFrequencyInMinutes 15

# Force replication
repadmin /syncall /AdeP

bash

Real-world Scenarios in an Organization

Branch with a slow line — its own Site + local DC so that login does not go over the WAN.
RODC in a physically insecure branch.

Troubleshooting

repadmin /replsummary — Replication status summary.
repadmin /showrepl DC01 — Details for each partner.
Event 1988 — Lingering Object, blocks replication until cleaned.

Glossary and Quick Command Line

KCC — Knowledge Consistency Checker.
ISTG — Inter-Site Topology Generator.
Tombstone Lifetime — 180 days by modern default.

Sites, Subnets, and Replication

What you will learn here

Active Directory replication between sites

Check yourself