[isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
- From: "Jim Harrison" <Jim@xxxxxxxxxxxx>
- To: <isapros@xxxxxxxxxxxxx>
- Date: Sat, 12 Aug 2006 08:54:36 -0700
I think you're confused; RPC/HTTP doesn't use MAPI; it's "just" HTTP
traffic.
AS such, any NSPI connections are strictly the problem of the BE server.
The only way ISA handles RPC traffic is via Exchange RPC or RPC (All
interfaces) rules.
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
On Behalf Of Jason Jones
Sent: Friday, August 11, 2006 5:13 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Exchange NSPI Proxy RPC Communications and ISA
Hi,
Bit of a shot in the dark, as this is a strange issue, but hoping
someone can confirm what I am seeing.
Basically, I have a pretty secure Exchange environment whereby both
Exchange FE's and BE's are on ISA protected perimeter networks with the
external network connected to the 'traditional LAN' e.g., ISA is acting
as a multinetwork internal firewall to specifically protect Exchange
from the internal network (all routed relationships). In this scenario,
ISA is controlling all communications to and from Exchange and all email
client access is published using web publishing or secure RPC
publishing.
Up until now everything has been working pretty well (apart from the
other RPC filter issues in my other posts!) but we have come across a
specific issue when using RPC/HTTP as follows:
The problem seems to lie with the fact that the back-end Exchange server
is talking to the GCs and ISA is seeing these connections as newly
initiated connections (e.g. non RPC) as opposed to detecting them as
dynamic ports which have been defined as part of the RPC handshake
process. Therefore, ISA is dropping these connections and prevents the
back-end server from communicating with the GCs, specifically for
RPC/HTTP (e.g. when using the NSPI proxy). All other communications
which relate to RPC and ISA's ability to detect dynamic RPC ports is
being done successfully (e.g. MAPI communications from Outlook to
Exchange). It looks to me as if the back-end Exchange server is
initiating it own connections which ISA sees as communications
independent of RPC. The issue only appears to arise when the back-end
servers proxy the client AD communication (e.g. when using the NSPI
proxy), as is the case with RPC/HTTP, because Outlook clients have no
access to the GCs from the Internet. For standard MAPI clients, they are
simply given a referral to the actual GCs which they communicate with
directly, independent of Exchange (e.g. not using NSPI proxy).
Does this sounds familiar? Is Exchange doing something weird here or is
ISA missing the RPC dynamic port negotiations?
Looking at the ISA logs, I see ports 1025, 1027, 1030 etc. being used by
the NSPI proxy which I am pretty sure are going to be the kind of ports
dynamic RPC would use. If I add the ephemeral ports (1024-65535) to the
existing BE=>GC rule everything work just fine. If I limit ports to
standard intradomain protocols including RPC then everything works apart
from RPC/HTTP and I start seeing ports 1025, 1027 etc. being denied by
ISA as unidentified traffic.
Answers on a postcard! ;-)
Cheers
JJ
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