When an EBGP router advertises a route to a neighbor in a different AS, it appends its own AS number to the AS_PATH attribute. This helps other routers recognize the path the route has taken and prevents routing loops.
If an EBGP router receives a route advertisement that already contains its own AS number in the AS_PATH attribute, it will drop the route. This prevents the router from accepting a route that would create a routing loop.

The Graceful Routing Engine Switchover (GRES) feature in Junos OS enables a router with redundant Routing Engines to continue forwarding packets, even if one Routing Engine fails.
GRES preserves interface and kernel information, ensuring that traffic is not interrupted.
However, GRES does not preserve the control plane.
To preserve routing during a switchover, GRES must be combined with either Graceful Restart protocol extensions or Nonstop Active Routing (NSR). When GRES is combined with NSR, nearly
75 percent of line rate worth of traffic per Packet Forwarding Engine remains uninterrupted during GRES. Any updates to the primary Routing Engine are replicated to the backup Routing Engine as soon as they occur.
Therefore, when GRES is combined with NSR, routing is preserved and the new master RE does not restart rpd.