In which scenario we will use SOO community , can you please eleborate with Diagram . I have some basic idea about it when AS path fail to avoid loop in EBGP we will use SOO but when this situation occur ?

Hello Tarun,

SOO uniquely identifies the site that originates a route. It is a BGP extended community that
prevents routing loops or suboptimal routing, specifically when a backdoor is present between
VPN sites. SOO provides loop prevention in networks with dual-homed sites (sites that are
connected to two or more PE routers). You can use it when an IGP is the PE-CE routing protocol.
You can also use it when BGP is used between PE and CE, when the as-path loop prevention
cannot be trusted anymore.( IT is one of the case ) This happens when BGP uses as-override or allowas-in.

If the SOO is configured for a CE router and a vpnv4 route is learned with the same SOO, the route must not be put in the VRF routing table on the PE and advertised to the CE