I have a=20 Linux box with RedHat 9.0 installed(eth0:218.xxx.xxx,eth1:192.168.0.1), = this box=20 is a firewall&proxy. Now I want external user can access my internal = web=20 server via the firewall box.

According to RedHat 9.0's manual and = the=20 posts in internet, I used the following command.

#iptables -t nat = -A=20 PREROUTING -p TCP -d xxx.xxx.xxx.xxx --dport 80 -j DNAT --to=20 192.168.0.5:80

But I can't access the internal web server from=20 outside.

Use tcpdump to get the following = packets:

21:57:18.274817=20 192.168.0.85.1331 > 218.77.120.200.25460: udp 49
21:57:18.450579=20 218.77.120.200 > 192.168.0.85: icmp: 218.77.120.200 udp port 25460=20 unreachable [tos 0xc0]
21:57:18.968829 192.168.0.5.netbios-ns >=20 192.168.0.255.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST;=20 BROADCAST
21:57:18.969963 0.00:30:48:23:04:33.455 >=20 0.ff:ff:ff:ff:ff:ff.455: ipx-netbios 50
21:57:19.057680 = 61.144.148.161.50660=20 > 192.168.0.5.http: S 5685372:5685372(0) win 8192 <mss=20 1452,nop,nop,sackOK> (DF)
21:57:19.718043 192.168.0.5.netbios-ns = >=20 192.168.0.255.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST;=20 BROADCAST
21:57:19.749255 0.00:30:48:23:04:33.455 >=20 0.ff:ff:ff:ff:ff:ff.455: ipx-netbios 50
21:57:20.468067=20 192.168.0.5.netbios-ns > 192.168.0.255.netbios-ns: NBT UDP = PACKET(137):=20 QUERY; REQUEST; BROADCAST
21:57:20.528584 0.00:30:48:23:04:33.455 = >=20 0.ff:ff:ff:ff:ff:ff.455: ipx-netbios 50
21:57:22.020715 = 61.144.148.161.50660=20 > 192.168.0.5.http: S 5685372:5685372(0) win 8192 <mss=20 1460,nop,nop,sackOK> (DF)
21:57:23.444576 arp who-has 192.168.0.85 = tell=20 192.168.0.1
21:57:23.444815 arp reply 192.168.0.85 is-at=20 0:e0:4c:ef:55:f8
21:57:23.533007 218.17.247.6.http > = 192.168.0.85.1383: R=20 562882410:562882410(0) ack 2793007952 win 0
21:57:24.054574 arp = who-has=20 192.168.0.5 tell 192.168.0.1
21:57:24.054674 arp reply 192.168.0.5 = is-at=20 0:30:48:23:4:33
21:57:27.919595 0.00:30:48:23:04:33.4010 >=20 0.ff:ff:ff:ff:ff:ff.452:ipx-sap-resp[|ipx 64]
21:57:28.024632=20 61.144.148.161.50660 > 192.168.0.5.http: S 5685372:5685372(0) win = 8192=20 <mss 1460,nop,nop,sackOK> (DF)
21:57:29.248044 = 192.168.0.100.netbios-ns=20 > 192.168.0.255.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST;=20 BROADCAST
21:57:29.248486 192.168.0.100.netbios-dgm >=20 192.168.0.255.netbios-dgm: NBT UDP PACKET(138)
21:57:33.839985=20 192.168.0.100.netbios-ns > 192.168.0.255.netbios-ns: NBT UDP = PACKET(137):=20 QUERY; REQUEST; BROADCAST
21:57:34.581878 192.168.0.100.netbios-ns = >=20 192.168.0.255.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST;=20 BROADCAST
21:57:35.332929 192.168.0.100.netbios-ns >=20 192.168.0.255.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST;=20 BROADCAST
21:57:40.026871 61.144.148.161.50660 > 192.168.0.5.http: = S=20 5685372:5685372(0) win 8192 <mss 1460,nop,nop,sackOK>=20 (DF)
21:57:43.191397 arp who-has 192.168.0.5 tell=20 192.168.0.4
21:58:18.987637 arp who-has 192.168.0.5 tell = 192.168.0.222=20

As I said, this box is a proxy too, so the above packets maybe = contain=20 un-useful messages to analysis where the problem is.

Anybody can = help me?=20