Nagios parents-problem

Hello,

I’ve got strange problem with controlling remote hosts in my network job.
Here is a problem:

gateway
(VPN)------------->INTERNET----------->remote router------------->terminal1 Access_Point1,2,3
(10.0.0.2)>>>>>>>>>>>>>>>>>>>>(external IP) >>>>>>> (10.6.0.199), (10.6.0.188),(10.6.0.233)
<<<<<<<<<<<<<<<<<<<<<<<<<<<<( 89.xx.xx.x:evil:

Nagios is behind router with gateway 10.0.0.2
Above I typed remote hosts (router, terminal1, all Access Point) which I want to monitor.
Here are objectets from hosts.cfg file:

define host {

    host_name               router_warszawa
    alias                   Router_Ilmet
    address                 89.xx.xx.xx.xx
    parents                 router_centrala    // name of gateway 10.0.0.2
    hostgroups              routery
    check_command           check-host-alive
    max_check_attempts      10
    check_interval          20
    check_period            24x7
    contact_groups          admins
    notification_interval   30
    notification_period     24x7
    notification_options    d,r,u,f
    notifications_enabled   0
    }

define host {

    host_name               terminal_warszawa
    alias                   Terminal-Ilmet
    address                 10.6.0.6
    parents                 router_warszawa // name of router with IP 89.xx.xx
    hostgroups              Serwerownia
    check_command           check-host-alive
    max_check_attempts      10
    check_interval          20
    check_period            24x7
    contact_groups          admins
    notification_interval   30
    notification_period     24x7
    notification_options    d,r,u,f
    notifications_enabled   0
    }

define host {

    host_name               AP2_warszawa
    alias                   AP2-Ilmet
    display_name            AP2-Ilmet
    address                 10.6.0.233        // name of Access Point
    parents                 router_warszawa
    hostgroups              punkty_dostepu
    check_command           check-host-alive
    max_check_attempts      10
    check_interval          20
    check_period            24x7
    contact_groups          admins
    notification_interval   30
    notification_period     24x7
    notification_options    d,r,u,f
    notifications_enabled   0
    }

And here is a result:

All of these remote hosts above are stated as DOWN
except of host “router_warszawa” which is UP.

What should I do to make rest of remote hosts visible for Nagios?
Should I make some port forwarding on “echo” or something like that?
Router is Linksys BEFSX41 and version of Nagios is 3.0

Kindly please for help,
Best regards