Monday 4 December 2017

ISTG (Inter Site Topolgy Generator)

ISTG:


Q What is ISTG ?
Answer: ISTG is nothing but a KCC server(DC), which is responsible for reviewing the inter-site topology and creating inbound
replication connection objects as necessary for bridgehead servers in the site in which it resides.The domain controller holding this role may not necessarily also be a bridgehead server.

Q TO generate the replication topology on the ISTG:
1> Determine the server that holds the ISTG role for the site. 
2> Open Active Directory Sites and Services: On the Start menu, point to Administrative Tools, and then click Active Directory Sites and Services. 
3> In the console tree, expand Sites, and then expand the site that contains the ISTG on which you want to run the KCC. 
4> Expand Servers, and then click the Server object for the ISTG. 
5> In the details pane, right-click NTDS Settings, click All Tasks, and then click Check Replication Topology. 
6> In the Check Replication Topology message box, click OK.

Q To generate Intersite replication topology?
A To generate the intersite replication topology, run the KCC on the domain controller in the site that holds the ISTG role.
Q To generate Intrasite replication topology ?
A To generate the intrasite replication topology, run the KCC on any domain controller in the site that does not hold the ISTG role.

Q Event 1009
A Event 1009 (informational): The consistency checker has started updating the replication topology for this server.

Q Event 1013
A Event 1013 (informational): The replication topology update task terminated normally.

Q How to increase Logging Level in KCC? What are it's merits & demerits ?
A The KCC, like all subsystems in Active Directory, has a variable event logging level. By default, only the most important events are logged. You can increase the level of detail in the event log by modifying the value in the Replication Events entry in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics in the registry.
Increasing the level of detail can be used to better understand the behavior of the KCC in different situations. However, a logging level value of greater than 2 generally results in excessive logging that degrades the performance of the component. Increasing the logging level can be useful for troubleshooting problems, but it is not recommended for normal operation

Q Intervals at whic KCC runs ?
A * 5 mins after the domain Controller starts: By default, the KCC runs its first replication topology check five minutes after the domain controller starts. This interval can be modified by changing the Repl topology update delay (secs) entry in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters as follows:
Value: Number of seconds to wait between the time Active Directory starts and the KCC runs for the first time.
Default: 300 seconds (5 minutes)
Data type: REG_DWORD
* services are running, the KCC checks the topology every 15 minutes : By default, as long as services are running, the KCC checks the topology every 15 minutes and makes changes as necessary. The administrator can modify the interval at which the KCC performs this review by changing the Repl topology update period (secs) entry in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters as follows:
Value: Number of seconds between KCC topology updates
Default: 900 seconds (15 minutes)
Data type: REG_DWORD

Q What happen if Current ISTG becomes unavailable ?
A If the current ISTG becomes unavailable for 60 minutes, an election is held by the other DCs in the site to appoint a new ISTG. This can sometimes cause problems for Active Directory replication

Q Default time for ISTG to establish new connection automatically between 2 sites if Primary ISTG server of either site fails ?
A 60 min

Q Mandatory Requirement for ISTG to be transferred to another server?
A It should be ADC(Additional Domain Controller)

Q To transfer ISTG role frm DC to other other Servers ?
A Open ADSIEDIT.msc
  1. Expand Configuration [DomainController].
  2. Expand CN=Configuration,DC=<domain>,DC=<com>.
  3. Expand CN=Sites.
  4. Highlight CN=<sitename> for the site where you want to change the ISTG Server.
  5. In the details pane, right-click on CN=NTDS Site Settings and select Properties.
  6. Locate the interSiteTopologyGenerator attribute and you will see which Domain Controller is designated as the ISTG server.
  7. To change the server, click Edit and then change the server name

Q To verify the replication ?
A repadmin /showrepl <servername> /u:<domainname>\<username> /pw:*

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