Short answer: Cisco’s VIC driver release notes first list nenic Geneve offload for ESXi in the 4.1(2a) driver release, which shipped nenic 1.0.33.0 for ESXi 6.7 U3 and 7.0. The 4.1(3a) release shipped nenic 1.0.35.0, which added ESXi 7.0 U1, plus the first nenic_ens driver for the NSX Enhanced Datapath. In UCS Manager, Geneve offload is disabled by default. You enable it per adapter policy on VIC 1400, 14000 or 15000. For ESXi 8, Cisco’s current driver is nenic 2.0.17.0.
I wrote the original post in January 2021 from the VMware download page for nenic 1.0.35.0 (ESXi 6.7). That page listed “Enabled Geneve Offload support for VIC 14xx adapters” as a new feature. The page has since been retired, and Cisco’s own release notes put the Geneve feature one driver release earlier. This update, from September 2026, follows the Cisco documentation.
Which nenic version introduced Geneve offload
| Cisco VIC driver release | ESXi nenic | Supported ESXi | Geneve note in the release notes |
|---|---|---|---|
| 4.1(1a) | 1.0.31.0 | 6.5 U3, 6.7 U2/U3 | none |
| 4.1(2a) | 1.0.33.0 | 6.5 U3, 6.7 U2/U3, 7.0 | New: “GENEVE Offload supports on ESX 6.7U3 and ESX 7.0” |
| 4.1(3a) | 1.0.35.0 | 6.5 U3, 6.7 U2/U3, 7.0, 7.0 U1 | New: “GENEVE Offload is supported on ESX 7.0U1”. First nenic_ens drivers: 1.0.2.0 (ESXi 6.7 U3) and 1.0.4.0 (ESXi 7.0, 7.0 U1) |
Cisco’s VIC 1400 best-practices white paper gives the same timeline from the firmware side. Geneve offload on the fourth-generation VIC is supported for ESXi “starting from Cisco UCSM and Cisco IMC release 4.1(2)”. Enhanced Datapath (ENS) support arrived with 4.1(3) and needs the additional nenic-ens driver.
So for NSX-T in standard (non-ENS) mode on VIC 1400, the minimum is the 4.1(2) firmware plus nenic 1.0.33.0. 1.0.35.0 is the version that brought ESXi 7.0 U1 support and the ENS path.
Enable nenic Geneve offload in UCS Manager
Per the UCS Manager 4.3 Network Management Guide, GENEVE offload is supported on ESXi with VIC 1400, 14000 and 15000 series adapters. It is present in all Ethernet adapter policies and disabled by default. Cisco’s recommended adapter policy for it:
| Setting | Value |
|---|---|
| Transmit queues / ring size | 1 / 4096 |
| Receive queues / ring size | 8 / 4096 |
| Completion queues | 16 |
| Interrupts | 32 |
| RSS | Enabled |
| GENEVE offload | Enabled |
For ENS, the VIC 1400 white paper recommends a single TX and RX queue with 4096 rings, and states that there is no RSS support on VIC 1400 for Geneve offload with ENS.
Limitations
- Not supported on VIC 1200 and 1300 series.
- External outer IPv6 is not supported with GENEVE offload.
- RoCEv2 cannot be used with GENEVE offload. Azure Stack QoS is also excluded.
- Remove the GENEVE offload configuration before downgrading to a release that does not support it.
Verify Geneve offload on the ESXi host
Broadcom KB 397644 shows how to confirm it. Look for VMNET_CAP_GENEVE_OFFLOAD under “Device Hardware Cap Activated”. In vmkernel.log, look for the nenic lines showing geneve yes and Geneve: Overlay offload enabled, udp_port = 6081:
vsish -e get /net/pNics/vmnic0/properties | grep "Driver\|Device Hard\|Device Soft"
# then check /var/log/vmkernel.log for the nenic Geneve linesThe same KB notes that the RX queue filter class for Geneve (the NetQueue Geneve filter) is not configured on nenic. That is expected: the filter is supported only by nenic_ens, and it is separate from checksum offload.
Current nenic versions for ESXi 8 and 9
| Cisco VIC driver release notes | nenic | nenic_ens | ESXi |
|---|---|---|---|
| 4.3(2), 4.3(4) | 2.0.11.0 (2.0.10.0 for 7.0 Ux) | 1.0.6.0 | 8.0, 8.0 U1 (7.0 U1–U3) |
| 4.3(6) | 2.0.17.0 | 1.0.9.0 | 7.0 U1–U3, 8.0 and above |
| 6.0(1) | 2.0.17.0 | 1.0.9.0 | 7.0 U1–U3, 8.0 and above |
| 6.0(2) | 2.0.17.0 | 1.0.18.0 | 8.0 and above |
Cisco’s VIC driver release notes say “ESX 8.0 and above” for nenic but do not name ESX 9.0 for it (the same document names ESX 9.0 for the fnic driver). Before you deploy on VCF 9, check the Broadcom Compatibility Guide for the exact nenic and VIC firmware pair certified for your ESX build.
Where to download nenic now
The old my.vmware.com download link no longer works. Async drivers are now on the Broadcom Support Portal, which requires a Broadcom account (see Broadcom KB 142814 on downloading Broadcom products). Use the Broadcom Compatibility Guide to pick the version.
Sources
- Release Notes for Cisco UCS VIC Drivers, Release 4.1
- Release Notes for Cisco UCS VIC Drivers, Release 4.3 and Release 6.0
- Cisco UCS VIC 1400 Series Best Practices in Ethernet Fabric (white paper)
- Cisco UCS Manager Network Management Guide 4.3: GENEVE offload
- Broadcom KB 397644: How to confirm Geneve offload configuration on nenic driver
- Broadcom KB 142814: Download Broadcom products and software
