Environment:
Red Hat OpenStack Platform 17.1 (OVN networking) Compute host: Broadcom NIC (bnxt_en driver), 25 GbE bonded uplinks Same host, same tenant network, same flavor — only the guest image differs
Problem: A VM booted from an Ubuntu cloud image gets only ~200-300 Mbps upload/download. A VM booted from a RHEL image on the same host and network gets ~8 Gbps. Roughly a 30x difference attributable solely to the guest image. Testing method: Multi-stream iperf3 (8 parallel streams), VM-to-VM. Platform capacity independently confirmed at multi-Gbps, so this is isolated to the Ubuntu guest. What I've already verified:
Network QoS policy allows 2 Gbps+ (not the limit) Physical NIC is 25 GbE with clean counters MTU is correct (1500 guest / geneve overlay) RHEL guest on the same host hits ~8 Gbps, so host/fabric is fine.
Question: What differs in the Ubuntu cloud image's default network configuration (virtio multiqueue, offload settings, driver/kernel) that would cause this large a throughput gap versus RHEL on the same virtio-net platform?