Branch office move: remote IP changing

Question

What happens to a site-to-site VPN when one of the end point IPs changes? 
 One of our branch offices is moving to a new location, and will change its external IP. We have an IPSec site to site VPN set up from our main offices to the branch office, which used X.509 certificates for authentication, and the VPN ID type is fqdn. Obviously, the VPN will break when the branch office's IP changes, but will this be easily fixable? That is, can I just update the IPs in the definitions used in the remote gateways secction, and have the VPN spring back to life again, or is it more complicated than that? 
 Would it be simpler just to scrap the current VPN setup, and create a new one once the IP has changed? 
 Any advice gratefully received!

sachingurung · Accepted Answer

Hi Davies, 
 Turn of the IPSec policy on both end, change the remote and local end gateways and turn ON the policy. It should work easily. 
 Thanks

BAlfson · Answer

Like Sachin says and you suspect, just change the IP and disable/enable the IPsec connection. If the Remote Gateway in the branch is set to 'Initiate connection' and the one in the main office is set to 'Respond only', you have nothing to change and the new branch location will come online immediately after the UTM boots up. 
 Cheers - Bob