CUCM is down

[Heba Ghonamy]

Our CUCM sub is suddenly down, not all our IP phone register from PUb

what should I do to reinstall the Sub without losing any data from PUB

what should I do to make all the phones register from PUB until reinstalling the SUB

Our CUCM Version 7.1.5.30000-1

[Nithin Eluvathingal]

I assume you have multiple device pools and cm groups. Change the device pool on the phone which use cmgroup which contain the publisher.
The phones which previously registers with the sub will register with publisher u till you rebuild the sub.

rebuilding must be need if the sub is not working.This would be possible if you have the bootable media kit for your 7.x version. 
if you don’t have the bootable image there won’t be any option as this version has reached EOL long back.

[Heba Ghonamy]

thanks for ur answer

should i reinstall the phones license again too

[Roger Kallberg]

No, as your Publisher is operational you will have all data present.

[Roger Kallberg]

This is very well described in the DRS backup and restore documentation. Advise you to read it and if you still have questions come back to this post with your specific question(s).

[Jonathan Schulenberg]

Also, at risk of stating the obvious: 7.1 reached end of software maintenance a decade ago this June. Immediately after you extricate yourself from this mess you need to begin planning an upgrade or migration to Webex Calling! That cluster is ancient and susceptible to a bunch of vulnerabilities at this point. It’s really startling to hear someone still has it in production TBH.