Boston Linux & Unix (BLU) Home | Calendar | Mail Lists | List Archives | Desktop SIG | Hardware Hacking SIG
Wiki | Flickr | PicasaWeb | Video | Maps & Directions | Installfests | Keysignings
Linux Cafe | Meeting Notes | Linux Links | Bling | About BLU

BLU Discuss list archive


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Discuss] web server can't see out but others can see in



> From: Edward Ned Harvey (blu)
>  
> Still, I think it's safe to conclude that your firewall is blocking both outbound
> ICMP and DNS.

A good test is like this:

ping 8.8.8.8
If it fails, you can conclude either ICMP is being blocked, or there's no route to host, or no return route.

nslookup google.com 8.8.8.8
This way, you're specifying directly, that you want to send the query to 8.8.8.8
If it fails, you can conclude either DNS is being blocked, or there's no route to host, or no return route.

On some other machine, pick a big name, like google.com, and nslookup that name.  Right now, I'm going to use 173.194.43.41 for google.com.
telnet 173.194.43.41 80
If it says "Connecting..." and hangs there, it means you have no route to host, or no return route.
If it makes a blank screen, where you can type, and you type in "get" and press enter and get a bunch of html, then you can conclude you have both a route to host, and a return route.

By process of elimination, the cause (or causes) of the problem is...




BLU is a member of BostonUserGroups
BLU is a member of BostonUserGroups
We also thank MIT for the use of their facilities.

Valid HTML 4.01! Valid CSS!



Boston Linux & Unix / webmaster@blu.org