Juniper Netscreen 25

I’m facing a problem with juniper firewall. our one site have Cisco 1841 with adsl wic having dynamic ip from isp. site two have cisco 1721 with static public ip on Ser0 and also static purblic ip in FE0. we creat a GRE tunnel between two sites. Site 2 also have juniper firewall connected on Cisco 1721 F/E0 and junper eth also have public ip. How to pass the site one traffice from juniper firewall to access the LOCAL LAN i.e. behind the junper firewall. Router to router communication is wroking fine. Can someone help me…..!