topic Promiscuous mode error on FTDv 7.6.2 in Network Security

Promiscuous mode error on FTDv 7.6.2

Knassi — Fri, 02 Jan 2026 15:21:27 GMT

I upgraded my FTDv to version 7.6.2 and when i try deploying policy, it failed with this error: error : ERROR: cannot set np to promiscuous mode.
ERROR: Failed to initialize interface, Add interface Failed.

Has anyone seen this and any workaround?

Thank you.

Re: Promiscuous mode error on FTDv 7.6.2

balaji.bandi — Fri, 02 Jan 2026 15:27:38 GMT

If this was worked on before the upgrade, it looks like a bug to me.

Or as underlay, ESXi, anything changed?

seen some error with bug before :

https://bst.cisco.com/bugsearch/bug/CSCvr11958

may be i try esxi vswitch - Promiscuous Mode to Accept

Re: Promiscuous mode error on FTDv 7.6.2

Knassi — Fri, 02 Jan 2026 15:56:36 GMT

There was no change on the ESXI host. We made sure the following are set:

Promiscuous Mode = Accept

MAC Address Changes = Accept

Forged Transmits = Accept

The bug was on version 6.4. The strange thing is that it is working at other sites

Re: Promiscuous mode error on FTDv 7.6.2

balaji.bandi — Fri, 02 Jan 2026 23:54:47 GMT

The strange thing is that it is working at other sites

then you should compare the setting if other site working same version same setup.

Re: Promiscuous mode error on FTDv 7.6.2

Cristian Matei — Sat, 03 Jan 2026 10:47:20 GMT

Hi,

So you're saying that with same version, 7.6.2, and same / similar config it works on other virtual FTD's but not on this specific one? Are both FTD instances, working one and not working one, hosted on same hypervisor type and version? Check if the non-working one uses same vNIC type as the working one. Have you tried also applying the patch for the version? Take a look here in vNIC's and drivers for 7.6.2:

https://www.cisco.com/c/en/us/td/docs/security/firepower/quick_start/consolidated_ftdv_gsg/threat-defense-virtual-76-gsg/m-ftdv-vmware-gsg.html

Thanks,

Cristian.