I have an IPSec tunnel to a customer location, very basic configuration on both ends. Tunnel is up, but for some reason I cannot ping the customer equipment unless he pings me first. I can reach each ip address only after I have been pinged from that ip address. I believe it has to be a firewall issue on their end, but the customer insists they are not blocking anything from us. Can anybody think of another reason this issue would take place? Thank you.