An A indicates that an Access Control List (ACL) is blocking the traceroute command traffic.
Identify the last-hop router in the traceroute command output. Check for any ACL configured on the last-hop router or next routers on the path to the destination.
For a complete list of characters that can be displayed in the traceroute command output, refer to The Traceroute Command section of Understanding the Ping and Traceroute Commands.
Multiple devices on different network
Default gateway can ping destination