As part of best practice I am planning to upgrade sip voice gateway IOS , need your advise whether I the current IOS version is still supported or upgrade is recommended in this case.
Note: There are no problems with the current version now.
Router Model: ISR4431/K9
What I recommend is take "Show Tech" and use it on CLI Analyzer tool. it give you more details about the current version and if there is any problems with ur existing device and you can decide.
Yes, it connect with the Cisco. you need to enter the Cisco ID. but it gives u detailed report regarding the issues with the version which u are using and even it point out if you are not following any best practice.
you can take the show tech file and use it on a machine which has internet access. use file analysis option. if you have "Show Tech File" install CLI on your machine and use the file analysis option.