The fax nsf CLI command was removed from the as5x gateways in the early 12.4 and 12.4T IOS versions because this command did not work for Nextport DSPs. The Nextport DSPs were found exclusively on the as5x platform. The as5x gateways using the Nextport DSPs either overwrote the NSF value to 0xff or passed it through unaltered regardless of what was configured using this command.
Current as5x voice gateways support the c5510 DSPs and no longer use the Nextport DSPs. Therefore, this command should technically work now if it was available in the CLI. I have not verified this personally but it sounds like the fax nsf command was not added back into the as5x images that now support the c5510 DSPs.
NSF issues are somewhat rare and if the value is being overwritten with 0xff, then you should not be running into problems with proprietary encodings.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.