Ari Luotonen, CERN, 1994

Configuring Proxy To Connect To Another Proxy

If there is a need to make an (inner) proxy cern_httpd connect to the outside world via another (outer) proxy server, you can use the same environment variables as are used to redirect clients to the proxy to make inner proxy use the outer one:

http_proxy
ftp_proxy
gopher_proxy
wais_proxy

E.g. your (inner) proxy server's startup script could look like this:

        #!/bin/sh
        http_proxy=http://outer.proxy.server:8082/
        export http_proxy
        /usr/etc/httpd -r /etc/inner-proxy.conf -p 8081

This is a little ugly, so there are also the following directives in the configuration file:

http_proxy http://outer.proxy.server/
ftp_proxy http://outer.proxy.server/
gopher_proxy http://outer.proxy.server/
wais_proxy http://outer.proxy.server/

no_proxy

In the same way that clients can specify a set of domains for which the proxy should not be consulted, httpd has a no_proxy configuration directive to tell it that it should not connect to another proxy for certain URLs:

        no_proxy  cern.ch,ncsa.uiuc.edu,some.host:8080

The argument string is a comma-separated list and should not contain spaces!

httpd@info.cern.ch