While I am adding devices it works if the IP range is of the same subnet of which IP assigned to librenms. While on other subnet it gives fail message while scan for SNMP. If we add device of other subnet for ICMP then it works fine.
Sorry, dont understand whats exactly your problem.
You can ping (ICMP) but cant SNMP? Do you have an ACL/Firewalled SNMP?
Yes correct while I add a device with ICMP I am able to add fine. If I add a device with SNMP it works with only the local subnet of which one IP is assigned to librenms server. I have multiple subnets and not able to add those subnets.I dont have any firewall.
Maybe snmp acl?
As @Daniel_Schmidt suggested, you may have the SNMP restricted by ACL or Firewall.
What device are you trying to add? Switch, Server, Workstation, etc?