IP address & firewalls query

[Operandi]

I am writing a web based PHP application to obtain performance reports from some networking equipment at various customer sites. This equipment will be behind their firewalls and proxy servers etc, but must be able to establish a connection to my web server on the Internet.

My app establishes a network connection to the equipments http/XML interface using fsockopen. My questions concern the access through the corporate firewalls required by my app ie:

As the fsockopen command is issued by the web server is the ip_address presented to the firewall the address of the server or the client?

Does the network admins only require the ip address of my web server to give users of the app access through the firewall or must he know the ip addresses of all clients that will be using the app?

Hope you can help

Chris

[dannys]

The IP address presented to the firewall will be that of the machine running PHP - i.e the server.

The client (user) connects to the webserver which does the fsock open and then sends the data back to the client. As far as the firewall is concerned, the client doesn't even exist - it's talking to the webserver.

[Operandi]

Thanks for replying so quickly Danny, and for the info. I actually have another couple of further questions about this ie;

In another part of the app, a graph is uploaded to the Internet client from the networking gear via its CGI interface. I can load this via <img src="remote.ip/?cgi etc.> Is this a direct connection between the client and the equipment (therefore the firewall sees the client ip address) or does this connection again originate from the web server?

By publishing the web server ip address to the customer so that they can "poke a hole" through their firewall for this ip address could cause problems should I need to change the ip address of the web server (moving to a dedicated server, or changing web hosting service etc). Is there a way of using web forwarding ie use a service such as freeparking.co.uk where you can redirect the client to the application at another ip address? In this case which ip address woiuld the firewall see - the redirection address or the actual address of the web server running the app? To make this a bit more clear

Client logs onto url.com at aaa.aaa.aaa.aaa
aaa.aaa.aaa.aaa is re-directed to the web server running the app at bbb.bbb.bbb.bbb

Thanks,
Chris