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DAG Network Configuration

Posted on 2013-11-22
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Last Modified: 2013-12-10
DAG Network Configuration

Our DAG is configured as shown in the snapshot.
it looks like each mailbox server has 2 Nics (2 IPs), in 2 different subnets.

I do not understand how they get the network heartbeat if the second NIC is not in the same subnets.

in the classic windows cluster we connect cat 5 from one Nic of the server to another NIC of the server and configure one(5.5.5.5) no subnet mask, the other (5.5.5.4) no subnet mask, that how we used to configure heartbeat.

I am not sure about the config shown in the snapshot.

Thank you
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Question by:jskfan
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LVL 37

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by:Mahesh
Mahesh earned 500 total points
ID: 39671209
Snapshot is missing..

Your comment:
"in the classic windows cluster we connect cat 5 from one Nic of the server to another NIC of the server and configure one(5.5.5.5) no subnet mask, the other (5.5.5.4) no subnet mask"

generally, exchange DAG members in same site remains in same subnet
for both production Network you should assign IPs of same subnet (say 10.1.40.0/24) with default gateway
for both heartbeat network (replication network), you should assign IPs of same subnet (differnt VLAN say 192.168.10.0/24) without default gateway

Check below link for full info
http://technet.microsoft.com/en-us/library/dd638129(v=exchg.150).aspx

Mahesh
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Author Comment

by:jskfan
ID: 39675787
Sorry..forgot the Snapshot:

DAG
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LVL 37

Assisted Solution

by:Mahesh
Mahesh earned 500 total points
ID: 39676748
Enabling replication on both subnets is not required

The network which used for production, just rename it as "Production"
The network which is without default gateway, rename it as "Replication Network"

Just keep replication enabled on subnet which do not have default gateway
If the replication network fails, the DAG will fail back to the MAPI (Production) network for replication.

Check below links for more info
http://blog.gothamtg.com/2012/09/26/configuring-dag-networks/
http://technet.microsoft.com/en-us/library/dd297927(v=exchg.141).aspx

Hope that helps
Mahesh
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Author Comment

by:jskfan
ID: 39687633
http://technet.microsoft.com/en-us/library/dd638104(v=exchg.150).aspx

I agree…I looked at the above link and on the diagram  it shows the Replication Network is on its own subnet and the MAPI Network is in its own subnet.

But I am not sure what makes one Network as Replication and the other as MAP network??

The old concept of clustering, there was Private and Public Networks, the private is usually a cat5 that goes from one NIC of one server to another NIC of the other server(that 's the Heart Beat)..
The public Network, connects the servers to the switch, so that servers communicate to the rest of the Network.

The snapshot I posted, it could be that both subnets connect to the switch.. so I am not sure what makes one subnet as Replication and the other Mapi.
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LVL 37

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by:Mahesh
Mahesh earned 500 total points
ID: 39688063
I already given answer in earlier comment

The network on which you have gateway, obviously clients (Mapi) will connect to that network only and this interface is also registered in DNS as well for identification.

Now another network left without gateway, you need to enable replication on this network explicitely so that exchange can understand that it needs to be used for replication.be aware that this interface is not registered in DNS purposely.
Since both servers IP addresses are listed in replication network as they are in same subnet, exchange will use that network for replication.

I don't know why in snapshot, repliation is enabled on both networks, which is not required
If the replication network fails, the DAG will fail back to the MAPI (Production) network for replication automatically regardless of checkbox.
Because it don't have any choice in that case as replication \ log shippping needs to be happened between DAG active and passive copies.

In case you want to strectch DAG across WAN network then its different story.Its doesn't apply to your scenario in question.
Just sharing link here FYI only.....i am not expecting any question on this in same post..
http://www.oakwoodinsights.com/collapsing-dag-networks/

Mahesh
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Author Comment

by:jskfan
ID: 39688202
since our Exchange servers are Virtual machines, how can I tell which subnet and interfaces are configured for MAPI and which are configured for Replication ?
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LVL 37

Assisted Solution

by:Mahesh
Mahesh earned 500 total points
ID: 39688269
let me know below information to answer your question

have you configured default gateway on both network cards mapi and replication ?

You need to check your hypervisor network card settings, do you have only one physical NIC on Hypervisor to which all your exchange servers virtual NICs are bridged ?
How hypervisor networking is setup ?

Out of two subnets, which is your production subnet ?

Mahesh
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Author Comment

by:jskfan
ID: 39688610
I will get this info Monday..
Thanks MaheshPM
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Author Comment

by:jskfan
ID: 39691316
I see :

Mailboxserver1 is in ESXserver11, and ESXserver11 has 2 physical NICs for VM port group
Mailboxserver1 is in 2 Vlans, it must have 2 virtual adapters that are in 2 different VLANs

Mailboxserver2 is in ESXserver13, and ESXserver2 has 2 physical NICs for VM port group
Mailboxserver2 is in 2 Vlans, it must have 2 virtual adapters that are in 2 different VLANs


ESXserver15 has 2 physical NICs for VM port group
ExchangeHub1 has one virtual NIC in one Vlan in ESXserver15

ESXserver12 has 2 physical NICs for VM port group
ExchangeHub2 has one virtual NIC in one Vlan in ESXserver12

To sum it up:

Mailboxserver1 has one NIC in Vlan 49 and one NIC in  VLAN 54
Mailboxserver2 has one NIC in Vlan 49 and one NIC in Vlan 54
ExchangeHub1 has one NIC in Vlan 49
ExchangeHub2 has one NIC in Vlan49

This might give you a good picture of the exchange connection
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Author Comment

by:jskfan
ID: 39691319
I could be wrong, but it seems like Vlan54 is what is called  Replication Network
and 49 is the MAPI Network...
Correct ?
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LVL 37

Assisted Solution

by:Mahesh
Mahesh earned 500 total points
ID: 39691915
Yes, you are right.
Your Virtual NICs VLAN Configuration states that VLAN 49 is the Production (MAPI) network

VLAN 54 must need to be used as Replication network only

You should disable replication on network adapters having VLAN 49 on mailbox server through DAG network.

Mahesh
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Author Comment

by:jskfan
ID: 39694180
I can do that..
however if I leave it the way it is configured now...I am not sure what is the downside of it.. it is working...

<<<You should disable replication on network adapters having VLAN 49 on mailbox server through DAG network.>>>
if I do not disable it , what would happen....?? it is working now with it enabled
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LVL 37

Accepted Solution

by:
Mahesh earned 500 total points
ID: 39694832
There is no impact.
You may do it post production HRS

Replication networks are optional. There can be multiple replication networks.

If the replication network fails, the DAG will fail back to the MAPI network for replication even if the MAPI network has it’s ReplicationEnabled property set to False

In the event of a failure affecting the MAPI network, a server failover will occur (assuming there are healthy mailbox database copies that can be activated).

Although a single network is supported, we recommend that each DAG have at least two networks: a single MAPI network and a single Replication network. This provides redundancy for the network and the network path, and enables the system to distinguish between a server failure and a network failure. Using a single network adapter prevents the system from distinguishing between these two types of failures.

http://technet.microsoft.com/en-us/library/dd638104(v=exchg.141).aspx

http://blog.gothamtg.com/2012/09/26/configuring-dag-networks/

Mahesh
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Author Closing Comment

by:jskfan
ID: 39710512
Thanks
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