Nagios Support Forum

There's not much more I can do without seeing a full network map, all settings for all interfaces, routers, gateways, firewalls, routing tables, and which interfaces can communicate and which cannot.

no firewall and no access control its simple network , other devices from same lan segment can communicate to other subnets but nagios secondary cannot ping /reachable from outside the subnets , i have tried from different destination but still same result. i am using nagios xi vmware platform whether it have any limitation in vmware platform for nagios or have to do any policy based routing to communicate multi interface. i am hosting natios in vmware server and ip /subnets are configured correctly as primary interface ip can communicate but secondary not able to ping from outside network.

Nagios XI is software simply installed on a minimal install of an OS(CentOS 7 in the case of our VM). You can rule out the nagios process by stopping it:
This sounds like a routing issue. Either the router isn't configured with the proper routes to handing the ICMP traffic or the Cent server needs a route added to send back to the non default interface.

if it routing issue enter subnets will face reachability issues from outside network. i think either centos not responding for icmp packets which have to define manually routes in nagios . when i add manually can reach from destination host to nagios secondary interface. Please note cannot add 100 network the destination manually .i expect it should work default way same like windows. one correction even the gateway not able to ping as earlier i have added a static route when i remove it gateway not able to ping from secondary interface and also when i deactivate primary interface secondary interface is working but when primary active secondary not working. kindly let me know whether any option or policy base routing both interface can reach from outside network

Note that you are not adding a route to nagios. You are adding a route to the CentOS.

one correction even the gateway not able to ping as earlier i have added a static route when i remove it gateway not able to ping from secondary interface and also when i deactivate primary interface secondary interface is working but when primary active secondary not working. kindly let me know whether any option or policy base routing both interface can reach from outside network

What is the end objective here? Can you share some details - network map, interfaces, IPs, etc... ? Maybe we can point you in the right direction.

i have inbox network and ip address details

I believe the problem you're running into is asynchronous routing. https://www.thomas-krenn.com/en/wiki/Tw ... One_System goes through setting up an environment like yours.