ORA-17627: ORA-12543: TNS:destination host unreachable ORA-17629: Cannot connect to the remote database server

[oracle@oracentd19c admin]$ rman target sys/sys@orclprim auxiliary sys/sys@orcldstdy|tee stdy.txt

Recovery Manager: Release 19.0.0.0.0 - Production on Tue Aug 22 06:13:15 2023
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle and/or its affiliates.  All rights reserved.

connected to target database: ORCL (DBID=1672814384)
connected to auxiliary database: ORCLS (not mounted)

RMAN> duplicate target database for standby from active database nofilenamecheck;

Starting Duplicate Db at 22-08-2023 06:13:21
using target database control file instead of recovery catalog
allocated channel: ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: SID=36 device type=DISK

contents of Memory Script:
{
   backup as copy reuse
   passwordfile auxiliary format  '/u01/app/oracle/product/19c/db_1/dbs/orapworcls'   ;
}
executing Memory Script

Starting backup at 22-08-2023 06:13:22
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=73 device type=DISK
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of Duplicate Db command at 08/22/2023 06:13:23
RMAN-05501: aborting duplication of target database
RMAN-03015: error occurred in stored script Memory Script
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 08/22/2023 06:13:23
ORA-17627: ORA-12543: TNS:destination host unreachable
ORA-17629: Cannot connect to the remote database server

RMAN>



from prim to standby 

from prod !!!
[oracle@oracent19c admin]$ tnsping orcldstdy

TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 22-AUG-2023 06:14:45

Copyright (c) 1997, 2019, Oracle.  All rights reserved.

Used parameter files:
/u01/app/oracle/product/19c/db_1/network/admin/sqlnet.ora


Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP) (HOST=192.168.0.56)(PORT=1521))(CONNECT_DATA=(SERVER=dedicated)(SID=orcls)))
TNS-12543: TNS:destination host unreachable







Check the firewall !!!!!

on standby 
[root@oracentd19c ~]# firewall-cmd --state
running
[root@oracentd19c ~]# systemctl stop firewalld     or add rule for 1521 
[root@oracentd19c ~]# firewall-cmd --state
not running
[root@oracentd19c ~]# systemctl disable firewalld
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
[root@oracentd19c ~]# firewall-cmd --state
not running


from prim now working !!
[oracle@oracent19c ~]$ tnsping orcldstdy

TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 22-AUG-2023 06:18:44

Copyright (c) 1997, 2019, Oracle.  All rights reserved.

Used parameter files:
/u01/app/oracle/product/19c/db_1/network/admin/sqlnet.ora


Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP) (HOST=192.168.0.56)(PORT=1521))(CONNECT_DATA=(SERVER=dedicated)(SID=orcls)))
OK (20 msec)
[oracle@oracent19c ~]$