Configuring Squid to Accelerate/ACL RPC over HTTP

Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.


Squid can be used as an accelerator and ACL filter in front of an exchange server exporting mail via RPC over HTTP. The RPC_IN_DATA and RPC_OUT_DATA methods communicate with https://URL/rpc/rpcproxy.dll, for if there's need to limit the access..


The example situation involves a single Outlook Web Access server and a single Squid server. The following information is required:

  • The IP of the Squid server (ip_of_squid)
  • The 'public' domain used for RPC Access (rpc_domain_name)
  • The IP of the Exchange (RPC) server (ip_of_exchange_server)
  • SSL Certificate to present to Exchange Server (/path/to/certificate)
  • SSL certificate to present to Clients (/path/to/clientcertificate)



This configuration MUST appear at the top of squid.conf above any other forward-proxy configuration (http_access etc). Otherwise the standard proxy access rules block some people viewing the accelerated site.

# Publish the RPCoHTTP service via SSL
https_port ip_of_squid:443 accel cert=/path/to/clientcertificate defaultsite=rpc_domain_name

cache_peer ip_of_exchange_server parent 443 0 no-query originserver login=PASS ssl sslcert=/path/to/certificate name=exchangeServer

acl EXCH dstdomain .rpc_domain_name

cache_peer_access exchangeServer allow EXCH
cache_peer_access exchangeServer deny all
never_direct allow EXCH

# Lock down access to just the Exchange Server!
http_access allow EXCH
http_access deny all
miss_access allow EXCH
miss_access deny all

Squid older than 3.1 also need to define several extension methods:

# Define the required extension methods
extension_methods RPC_IN_DATA RPC_OUT_DATA

Thanks to

Thanks to Tuukka Laurikanien <> for providing the information used in preparing this article.


ConfigExamples/Reverse/ExchangeRpc (last edited 2011-10-06 11:51:48 by AmosJeffries)