[isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
- From: "Jim Harrison" <Jim@xxxxxxxxxxxx>
- To: <isapros@xxxxxxxxxxxxx>
- Date: Sat, 12 Aug 2006 17:42:35 -0700
Ah, yes.
While this is a desirable design, it's also a very difficult one.
What are the network relationships between the networks?
For instance:
ExchFE ßà Exch BE == Route
...?
Have you disabled Strict RPC on the relevant rules?
NAT ain't happenin' FWIW...
What's the "Internet FW"?
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jason Jones
Sent: Saturday, August 12, 2006 3:18 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
________________________________
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jim Harrison
Sent: 12 August 2006 22:41
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
Maybe a napkin drawing, then?
I don't understand how your BE needs specific rules unless its separated from
the DC by ISA?
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jason Jones
Sent: Saturday, August 12, 2006 2:19 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
No, not confused, and realise the difference between RPC/HTTP and MAPI. I guess
I am obviously not explaining myself very well with a complex environment and
the problem very specific.
>>AS such, any NSPI connections are strictly the problem of the BE server.
Not in this scenario, as the BE is in an ISA protected network seperated from
the DCs and FEs. The rule that allows access from BE=>DCs is using RPC (All
interfaces) and yet ISA is blocking traffic from the NSPI proxy when using
RPC/HTTP. All other RPC traffic from BE=>DCs is working as expected and ISA is
detecting the RPC dynamic ports correctly.
If I allow All outbound protocols from BE=>DCs the NSPI proxy works and I see
ports 1025. 1026 etc being used. It seems as if ISA is missing the intitial RPC
negations between the NSPI proxy and DCs and hence blocks all dynamic ports
after 135 is contacted.
Maybe I need to provide some diagrams and/or better desacirptions...
JJ
________________________________
From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jim Harrison
Sent: 12 August 2006 16:55
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: Exchange NSPI Proxy RPC Communications and ISA
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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