It is important to configure the network adapter settings correctly for a DAG member. Few points that need to be noted:
- Single NIC for DAG members is supported.
- All DAG members should have the same number of networks, MAPI and Replication networks.
- DAG members can have only one MAPI network and zero or more Replication networks.
- Persistent static routes are used to configure traffic in a replication network.
- It is recommended to have atleast two DAG networks, MAPI and a replication network.
The MAPI network should be connected to the production network, so that it can talk with other Exchange servers, AD, DNS etc. The MAPI network (NIC) should be configured as given in the table below.
| Networking Features | Setting |
| Client for Microsoft Networks | Enabled |
| QoS Packet Scheduler | Optionally enable |
| File and Printer Sharing for Microsoft Networks | Enable |
| Internet Protocol Version 6 (TCP/IP v6) | Optionally enable |
| Internet Protocol Version 4 (TCP/IP v4) | Enabled |
| Link-Layer Topology Discovery Mapper I/O Driver | Enabled |
| Link-Layer Topology Discovery Responder | Enabled |
Configure the following as well for the MAPI network.
- The IP address can be manually assigned or configured to use DHCP. If DHCP is used, use persistent reservations for server’s IP address.
- The MAPI network typically uses a default gateway, although one isn’t required.
- At least one DNS server address must be configured. Using multiple DNS servers for redundancy.
- The “Register this connection’s addresses in DNS” checkbox should be checked.
The Replication network (NIC) should be configured as given in the table below.
| Networking Features | Setting |
| Client for Microsoft Networks | Disabled |
| QoS Packet Scheduler | Optionally enable |
| File and Printer Sharing for Microsoft Networks | Disabled |
| Internet Protocol Version 6 (TCP/IP v6) | Optionally enable |
| Internet Protocol Version 4 (TCP/IP v4) | Enabled |
| Link-Layer Topology Discovery Mapper I/O Driver | Enabled |
| Link-Layer Topology Discovery Responder | Enabled |
Configure the following as well for the MAPI network.
- The IP address can be manually assigned or configured to use DHCP. If DHCP is used, use persistent reservations for server’s IP address.
- The Replication network typically doesn’t use a default gateway. If MAPI network has a gateway configured, then, no other networks should have a default gateway.
- DNS server address should not be configured.
- The “Register this connection’s addresses in DNS” checkbox should be unchecked.
Finally, the binding order has to be such that MAPI network comes first in the list.
Please let me know if you have any questions in the comments section.
Very useful article, thank you!
Thanks Natesh.
Hello Rajita,
How can I configure MAPI and Replication networks on single NIC? and is it possible to use Two NICs on some DAG members and only one NIC on the other members.
Hi Sayed,
If you only have one NIC, have all the production details on it and Exchange will use it for Prod and replication. You don’t need further config, it just works.
You cannot have a DAG in which few servers have one NIC and few others with replication NICs.
And it’s Rajith ;)
Thanks Rajita.
Glad to help Sayed
HiRajith,
Thanks for your post . However I have some problem with this which I described below. Can you help me with this.
I have configured the NIC settings as described above. However I am seeing the traffic between Primary and DR site consuming some bandwidth via MAPI network.
I checked network statistics for the process msexchangerepl.exe it establish connection via replication port (64327) which passes via Replication network well . But also the same process using diferrent random port which passes the network traffic via MAPI wan link. Can we use the Replication link instead of MAPI by the entire process(msexchangerepl.exe) used traffics.
Hi Mounish,
Replication should be enabled for the Replication network and DISABLED for MAPI network
Thank you very helpful and easy to follow!
Thanks Anthony.
Is it possible to run DAG, if the Mapi and REplication NEtwork have the same networkspace?
For example:
Mapi: 192.168.1.50
REplication: 192.168.1.51
Regards
Hi Sunshine,
The whole point is to separate the traffic. If they are on the same subnet and taking the same path, you might as well use the MAPI NIC for replication as well. No need to have a separate NIC for replication.
The above setting are understood. But how DAG sence that he has to use to Replication NIC's not MAPI
In the DAG network you can choose if the Network replicates.
If you don’t check the box it is solely used for MAPI.
Anthony,
Check http://www.theucguy.net/2011/10/what-happens-when-replication-network.html
Is the binding order of all NICs correct, the third one being last?
We have added a third network connection (iscsi) which seems to have broken the DAG. The DAG networks now show as missconfigured. Any ideas?
Thanks Anonymous
Really REALLY helpful. Can't thank you enough.