Cisco CallManager Restriction for backup route group

[orkhan.rustamli.96]

Hello, Everyone. I almost finished my study of working with CUCM in beginner level. I learned how to configure route (dial-peer) with 3 level architecture RouterGoup -> RouterList -> RouterPattern. I understood that different route group can be used as fallback, backup way for destination (If WAN is down, using PSTN connection for branch office, etc.) My question how do I configure class of control for backup channel. I mean if WAN is working, everyone can use both WAN and PSTN connections with with given CSS to them. But if WAN is down, only certain persons can use PSTN connection for calling branch office numbers.

Thanks in advance

[Dennis Mink]

need to know a little more about your set up. how are users in a certain branch reaching PSTN? through some sort of centralised GW?  also, have you got SRST configured that phones register to when WAN is down?