There are several Windows 10 machines with 1 Gbps and 40 Gbps network cards, both of which are connected to the same router. The router has four networks: WAN, C, A, and B (which corresponds to the network cards on the Windows 10 machines). Routing is possible between A, B, and C, and A is configured as the gateway.

From network C, there are issues communicating with network A. It seems that packets are initially routed correctly, but then they are routed through the faster network B, which causes problems for the Windows 10 operating system when it receives responses from an address it did not connect to. These responses are dropped and communication hangs.

It’s worth noting that even though the communication started on network A, the machines on networks A and B are switching routes back to network C through network B. This is not a routing problem, as everything can ping everything, and it is not a connectivity problem either. For example, it is possible to RDP from network C into networks A and B, but only the connections to network B are stable. Connections to network A initially work, but then hang after a few frames (packets?).

CIFS file copies have no issues, but it’s important to note that Windows is designed to route copies across the fastest routes. Only Windows 10 machines seem to have this issue, as Windows Server expects multi-homing and does not behave in this way.

It’s clear that there is a configuration issue causing the machines to switch interfaces. Is there a way to fix this, while still allowing the option to use the faster route on network B if needed for improved performance on CIFS?

Askify Moderator Edited question May 4, 2023