ping linux machine from outside router

hi all,

I have one strange problem in the network.

here is rough network diagram ...

LAN1 -- ROUTER1 -- LEASE LINE -- ROUTER2 -- LAN2

now i have 2 linux machines ... one in LAN1 and one in LAN2.

linux machines have 2 ethernet cards .. one for ISP and one for LAN. each have default gateway set to ISP's gateway provided by them.

now any machine in LAN1 can't ping LAN2's linux machine and same thing for LAN2 that any machine from LAN2 can't ping LAN1's linux machine.

but yes machines in LAN1 can ping linux machines in LAN1 and same for the LAN2 machines. and there is no firewall [iptables service is stopped]. and no script is running related to it.

I did try to stop iptables so that firewall not come in the picture ... but still no luck. should i have to add some routes in those linux machines regarding these routers etc.,

thanks for your help in advance.

regards,

Ashvin Savani (arckid)