Exchange 2010 DAG IP Address

I've recently started working for a company that uses an Exchange 2010 DAG.  However, no DAG IP address is configured in the EMC, yet the system seems to fail-over correctly during an outage.  What is the purpose of this setting within the EMC?
DAGIP.JPG
tballinAsked:
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EEhotlineCommented:
If you haven't specified an IP address for the DAG then it will be assigned by DHCP. The IP address is used by the underlying Windows Failover Cluster Service to determine DAG availability.

More info from here: http://technet.microsoft.com/en-us/library/dd979799.aspx
dsnegi_25decCommented:
its a default nature for DAG if you will not assigned static IP so it will automatically pick from the DHCP.

And it's a similar to Ex2007 VIP address which is used to failover/swithcover the node
Suliman Abu KharroubIT Consultant Commented:
You can check/set DAG ip address using EMS:

http://technet.microsoft.com/en-us/library/dd297985(v=exchg.150).aspx
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tballinAuthor Commented:
An IP address has been assigned through the Failover Cluster Manager, and that is the address that always gets assigned to the active DAG member.  However, when I use the EMS (Get-DatabaseAvailabilityGroup) to determine the DAG IP address, here is what I get:

Name                                   : ACMEDAG
Servers                                : {ACMEEXG10site1, ACMEEXG10site2}
WitnessServer                          : ACMEads1.domain1.local
WitnessDirectory                       : c:\DAG-FSW
AlternateWitnessServer                 :
AlternateWitnessDirectory              :
NetworkCompression                     : InterSubnetOnly
NetworkEncryption                      : InterSubnetOnly
DatacenterActivationMode               : Off
StoppedMailboxServers                  : {}
StartedMailboxServers                  : {}
DatabaseAvailabilityGroupIpv4Addresses : {}
DatabaseAvailabilityGroupIpAddresses   : {}
AllowCrossSiteRpcClientAccess          : False
OperationalServers                     :
PrimaryActiveManager                   :
ServersInMaintenance                   :
ServersInDeferredRecovery              :
ThirdPartyReplication                  : Disabled
ReplicationPort                        : 0
NetworkNames                           : {}
WitnessShareInUse                      :
AdminDisplayName                       :
ExchangeVersion                        : 0.10 (14.0.100.0)
DistinguishedName                      : CN=ACMEDAG,CN=Database Availability Groups,CN=Exchange Administrative Group (FYDIBOHF23SPDLT),CN=Administrative Groups,
                                         CN=ACMEElgin,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain1,DC=local
Identity                               : ACMEDAG
Guid                                   : 0c4b1047-c2a0-463b-bf02-3098dc4c2301
ObjectCategory                         : domain1.local/Configuration/Schema/ms-Exch-MDB-Availability-Group
ObjectClass                            : {top, msExchMDBAvailabilityGroup}
WhenChanged                            : 06/28/2011 12:12:53 PM
WhenCreated                            : 06/28/2011 12:11:29 PM
WhenChangedUTC                         : 06/28/2011 05:12:53 PM
WhenCreatedUTC                         : 06/28/2011 05:11:29 PM
OrganizationId                         :
OriginatingServer                      : ACMEADS2.domain1.local
IsValid                                : True

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So it seems that the DAG IP setting in Exchange is not really needed, and that the only thing that matters is the IP address setting in the Cluster Core Resources section of the Failover Cluster Manager.  If that's really the case, why is there a DAG IP address option in Exchange?
EEhotlineCommented:
You can look here to see why a Dag's IP is needed:

http://www.msexchange.org/blogs/walther/news/setting-static-ip-addresses-for-a-dag-using-the-gui-in-exchange-2010-sp1-techtip-3-513.html

http://www.shudnow.net/2010/09/27/exchange-2010-site-resilience-multiple-dag-ips-and-cluster-resources/

I believe most people would like to assign a static IP to their servers, or at least I do. I don't want DHCP handles that part for important servers.
tballinAuthor Commented:
That's the thing, while I understand the need for the DAG IP, this system seems to work without it.  Why is that?

In our case, the active DAG member appears to use the static IP set from within the Failover Cluster Manager (Under Cluster Core Resources, Cluster name, IP address).  And to be clear, DHCP is not used.



FCM Cluster IP Setting
Suliman Abu KharroubIT Consultant Commented:
The correct and recommended way to configure the dag settings is using emc or ems not working directly with failover cluster console.
tballinAuthor Commented:
So I'm wondering then what the consequences are of not configuring the DAG IP setting in Exchange.  It may be a best practice, but from what I can tell, not having DAG IP configured in Exchange seems to have no effect whatsoever.  

My question more specifically is, what are the hazards of not configuring the DAG IP in Exchange?  In what ways will system performance be degraded if I don't configure a DAG IP in Exchange?

The answer I'm looking for would sound something like: "If you only configure a static IP in the failover cluster manager and not in Exchange, you will experience the following problems: problem X, problem Y and problem Z"
EEhotlineCommented:
I believe you have the static IP for your DAG, it's just you have set it from Failover Cluster Manager instead of from EMC.

By default the DAG will get assigned an IP through DHCP but it is best practice to assign a static address and put it into DHCP reservation if required.  You don’t want to run into a situation where your DHCP gets full and your DAG cannot pick up an IP address.

The only reason why they exist is because Failover Clustering requires an IP Address for the Cluster Group. And the reason why the cluster group needs an IP Address is that if a CNO doesn’t have an active IP respond for it every 30 days (or whatever the value is configured for) the CNO gets cleaned up.

More info from here:

http://technet.microsoft.com/en-us/library/dd638104%28v=exchg.141%29.aspx

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tballinAuthor Commented:
I'm still a little fuzzy on what Exchange does with the DAG IP address that get's configured in its DAG IP address field, but I've belabored this long enough.
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