Refer to the exhibit:When implementing an LDP protocol, an engineer experienced an issue between two...

The issue of no LDP neighbor existing for 1.1.1.1 between two directly connected routers could be due to R2 not receiving any hellos from R1. In the context of LDP (Label Distribution Protocol), hellos are used for the discovery of LDP peers. They are sent periodically on each interface that LDP is enabled on to discover and maintain LDP sessions with neighbors. If R2 is not seeing any hellos from R1, it means there’s a failure in the initial step of establishing an LDP session, hence no neighbor relationship is formed.