To configure redundant paths for your outbound calls, you can simply add two or more Gateways/SIP trunks to your Route Group.
A Standard Local Route Group, on the other hand, does not play any roles in creating call path redundancy but rather it's a useful feature for reducing the number Route Lists and Route Patterns in large clusters with numerous locations/PSTN connections.
Let's say you have 20 sites (1 HQ and 19 Remote sites) whithin the same CUCM cluster, and each site has its own gateway/PSTN connection.
In this scenario, WITHOUT the use of Standard Local Route Groups, you would need to create 1 route group, 1 Route List, and at least 3 route patterns (i.e Local, Long Distance, Emergency and etc.) for EVERY single location.
This means a total of 20 Route Groups, 20 Route Lists and at least 60 Route Patterns. It can get very messy and even worse as the number of your sites grow. This is where Standard Local Route Groups come in.
With the use of Standard Local Route Groups, in the scenario above, you would still need 20 Route Groups, but only 1 Route List and 3 or a few more Route Patterns for the entire cluster, NOT for every location anymore.
Example below shows the usage of Standard Local Route Group in a cluster with only two sites but the concept is the same for any number of sites.
HQ_Route_Group
First path= HQ_Gateway
Second path= RemoteSite_Gateway
RemoteSite_Route_Group
First path= RemoteSite_Gateway
Second path= HQ_Gateway
SLRG Name
Standard Local Route Group
All_Site_Route_List
Route Group= Standard Local Route Group
9.[2-9]XX[2-9]XXXXXX
Route List = All_Site_Route_List
91.[2-9]XX[2-9]XXXXXX
Route List = All_Site_Route_List
911
Route List = All_Site_Route_List
HQ_ Device_Pool
Local Route Group = HQ_Route_Group
Site B Device Pool
Local Route Group = RemoteSite_Route_Group
Hope this helps answer your question.
