Outside Host cannot access my computer

[hanxue]

Recently, I started having network problems. My PC is currently connected to a local LAN (uni. campus), and I access the Internet through a proxy server.

I do not have any problem connecting to outside hosts, including PCs in the same network and also the Internet. A file sharing problem using TCP and UDP is also working fine.

The problem is, outside host cannot access my PC. I run an Apache server and any computers inside the LAN cannot access my PC. But I can access other PCs running Apache. (view their websites).

Also, I can connect to a UNIX server which is located in the same LAN. I telneted there, but from there, I cannot ping my own computer!

Whenever I tried pinging myself remotely, or ask a friend (inside the LAN) to ping me, I can see the "incoming packet" part of the network icon in System Tray blinking, but but no "outgoing packet".

I disabled all firewalls now.

Below is my IPConfig info:

Windows 2000 IP Configuration

Host Name . . . . . . . . . . . . : win2k
Primary DNS Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : Yes
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : dyn.monash.edu.au

Ethernet adapter Local Area Connection 2:

Connection-specific DNS Suffix . : dyn.monash.edu.au
Description . . . . . . . . . . . : D-Link DFE-538TX 10/100 Adapter #2
Physical Address. . . . . . . . . : 00-05-5D-4C-48-26
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 130.194.197.227
Subnet Mask . . . . . . . . . . . : 255.255.224.0
Default Gateway . . . . . . . . . : 130.194.199.254
DHCP Server . . . . . . . . . . . : 130.194.15.1
DNS Servers . . . . . . . . . . . : 130.194.1.99
130.194.7.99
Primary WINS Server . . . . . . . : 130.194.196.29
Lease Obtained. . . . . . . . . . : Friday, 22 August 2003 11:53:42 PM
Lease Expires . . . . . . . . . . : Saturday, 23 August 2003 11:53:42 AM

What might be the problem?


Thank you very much in advance.

[Spider]

I would expect the uni has shut the port down from outside access
because of the RPC exploit that is presently moving around.

I doubt calling the help desk will verify this unless you can talk
to the sys admin themselves. Most help desk phone staff are
volunteer students and not privy to the inner workings of the
servers.

[hanxue]

I would expect the uni has shut the port down from outside access
because of the RPC exploit that is presently moving around.

I doubt calling the help desk will verify this unless you can talk
to the sys admin themselves. Most help desk phone staff are
volunteer students and not privy to the inner workings of the
servers.

Thanks! I think that is a very useful tip.

But I think it does not apply to my case. The reason is, I can access my friend's PC, ping it, access port 80 (and read webpages), but he can't do the same to mine.

I even portscanned my PC. It showed ports 21, 80, 100, 138, 139, 411 open.

When I use my web browser to access my own IP address (real IP, not 127.0.0.1), I can't access it either. But 127.0.0.1 works.

I really could not figure out what is wrong.

[Spider]

But I think it does not apply to my case. The reason is, I can access my friend's PC, ping it, access port 80 (and read webpages), but he can't do the same to mine.
Don't confuse outbound with inbound. This is exactly what filtering is, it
lets things out but not in.

I even portscanned my PC. It showed ports 21, 80, 100, 138, 139, 411 open.
Again, don't confuse your computers ports with the WAN's (uni's) ports.
Just because your computers 138 is open doesn't matter if the uni is
blocking it's 138. That means the uni can access your 138 but anything
on the otherside of the uni will not be able to.

When I use my web browser to access my own IP address (real IP, not 127.0.0.1), I can't access it either. But 127.0.0.1 works.
I really could not figure out what is wrong.
I don't think I quite understand what your explaining here. Your running
a port 80/8080 server?

[hanxue]

Don't confuse outbound with inbound. This is exactly what filtering is, it
lets things out but not in.

Again, don't confuse your computers ports with the WAN's (uni's) ports.
Just because your computers 138 is open doesn't matter if the uni is
blocking it's 138. That means the uni can access your 138 but anything
on the otherside of the uni will not be able to.

I don't think I quite understand what your explaining here. Your running
a port 80/8080 server?

Yes, I am running HTTP server on ports 80, 90 and 100.

The thing is, I can access my friend's port 80, but not vice versa. I can ping him, but he can't ping me. That is why I think it is my PC with the problem.

[Spider]

I'm sure the uni doesn't allow you to run a server. Who is going to pay the bandwidth?
What, for instance, if you served 5 million mp3s and you had 20,000 users on at any time?
And how is the uni to know the difference if you serve *.doc to friends or pirate mp3s?
They will most certainly have in place restrictions on the service to student.

You have to remember where your getting your Internet service from. This is a university
and not a clean T1 line.
That is why I think it is my PC
Like Morpheus said in The Matrix..."Open your mind".