Note that urpmi will use system global proxy settings (cf environment variable "http_proxy" or "ftp_proxy"). If you don't want urpmi to use any proxy, you can use "http_proxy=" or "ftp_proxy=".
[media:]http_proxy=[value]
[media:]ftp_proxy=[value]
[media:]proxy_user=[value]
where the media part is optional (in this case, the line applies to all media). ftp_proxy and http_proxy values have the same syntax as the usual environment variables used by many programs such as curl(1):
[protocol://]<host>[:port]
"proxy_user" values are simply a user name, or a user name and a password separated by a colon (":").
Alternatively, instead of "proxy_user", you can write:
[media:]proxy_user_ask
In this case, urpmi and other tools will prompt for proxy credentials (like with the urpmi command-line option --proxy-user=ask).