Does changing the LTM root/admin password affect GTM / Big IP DNS?
Does changing the LTM root/admin password affect GTM / Big IP DNS? Is there any impact/outage expected? Do I need to do bigip_add command again for all the LTMs? Thanks!
No, there shouldn't be any outage if you only change the password. Once iQuery communication is established between the LTM and GTM's, any further communication is happening using the device certificates (https://support.f5.com/csp/article/K15664), rather than the passwords.
Of course, I've got no insight in your specific configuration, so always a good idea to doublecheck, but I wouldn't expect any outage.
Hope this helps.