I have two Windows Server 2019 Datacenter Edition servers, each with RDMA-enabled Mellanox ConnectX‐4 Lx 25GbE DA/SFP NICs. I've directly connected them with a 1 meter SFP28 copper cable.
**How can I get them to see each other?**
The cards try to negotiate and wind up with APIPA addresses.
I read that setting static IPs without a default gateway would work as long as they are on the same subnet, but doing so doesn't seem to work (can't ping each other; [`Test-Cluster`](https://docs.microsoft.com/en-us/powershell/module/failoverclusters/test-cluster?view=win10-ps) fails).
Two-node, switchless setups are supported configurations (see [Storage Spaces Direct hardware requirements](https://docs.microsoft.com/en-us/windows-server/storage/storage-spaces/storage-spaces-direct-hardware-requirements)):
I can't find any examples of Microsoft or anyone else discussing such a setup. Maybe I don't know what to search for, as I've never used this type of NIC before. I would really like to avoid having to buy a switch for them.
How can I get these two NICs to ping each other without a switch?
Configuration réseau sans commutateur pour deux nœuds directement connectés ?
Re: Configuration réseau sans commutateur pour deux nœuds directement connectés ?
To enable DA NICs to communicate with each other, simply assign IPs and subnet and leave gateway and dns server fields blank. For example
Node 1
```
IP: 192.168.10.1
SubnetMask: 255.255.255.0
```
Node 2
```
IP: 192.168.10.2
SubnetMask: 255.255.255.0
```
If NICs still try to use APIPA, then just remove device/drivers form device management and reinstall NICs drivers.
2-node S2D is broken and can’t survive second node reboot / down w/out losing pool quorum and disconnecting S2D pool. This is known issue and has to be fixed around this fall with some of the fixes (not guaranteed time frame). [Example thread](https://social.technet.microsoft.com/Forums/windowsserver/en-US/f09dbb64-dd64-4e2f-a9d3-7375b7be81b3/s2d-on-2019-perhaps-a-bug?forum=winserverClustering#b243262d-5e1a-42e0-bae1-b9b8ed8eda3c) with an issue.
If you need 2-node switchless configuration, look at solutions, which have been designed for such setup. Like [Starwind vsan](https://www.starwindsoftware.com/resource-library/starwind-virtual-san-for-hyper-v-2-node-hyper%D1%81onverged-scenario-with-windows-server-2016)
Node 1
```
IP: 192.168.10.1
SubnetMask: 255.255.255.0
```
Node 2
```
IP: 192.168.10.2
SubnetMask: 255.255.255.0
```
If NICs still try to use APIPA, then just remove device/drivers form device management and reinstall NICs drivers.
2-node S2D is broken and can’t survive second node reboot / down w/out losing pool quorum and disconnecting S2D pool. This is known issue and has to be fixed around this fall with some of the fixes (not guaranteed time frame). [Example thread](https://social.technet.microsoft.com/Forums/windowsserver/en-US/f09dbb64-dd64-4e2f-a9d3-7375b7be81b3/s2d-on-2019-perhaps-a-bug?forum=winserverClustering#b243262d-5e1a-42e0-bae1-b9b8ed8eda3c) with an issue.
If you need 2-node switchless configuration, look at solutions, which have been designed for such setup. Like [Starwind vsan](https://www.starwindsoftware.com/resource-library/starwind-virtual-san-for-hyper-v-2-node-hyper%D1%81onverged-scenario-with-windows-server-2016)