In
today’s secure corporate WAN networks one common issue I see on a regular basis
is Exchange connected Outlook clients not working because of corporate firewall
changes or misconfiguration.
Properly
the quickest way to check if a firewall is blocking or filtering rcp traffic
between you outlook client and an exchange server is to use the PortQry.exe
tool. This Windows Server Support tool sends packets to specified ports and
looks to see if that port has been blocked (filtered).
To
begin install the Server Support tools from your Windows Server CD for your
version of Windows Server once installed, or download the new version PortQry
version 2 from the following location.
PortQry
Version 2 Download
If
you are a GUI type person you can also download the PortQueryUI tool from the
below location
PortQueryUI
PortQry GUI Download location
Using
the PortQry or PortQueryUI tool returns the below values depending on the state
or filtered state of the destination servers port
Listening
Some Process is running on the port you have queried
Not
Listening
No process is running on the port you have
queried
Filtered
The port queried has been blocked (filtered)
To
use PortQry to check for filtered rpc ports we first need to understand how rpc
works, firstly an initial connection is made over port 135 after which a random
port between 1024 and 65535 is negotiated for
the main communication.
If
you were issuing checking a standard ports status you would run the following
command from the command prompt:
portqry -n ServerName
-e 135
Figure 1 "Output from PortQry Tool"
It
is most likely that port 135 will be listening and not filtered, but one of the
endpoints between 1024 and 65535 are blocked, so now you need to check
the output above taking note of each of the endpoint ports, after this you can
use portqry again using the -o switch to specify each of the individual
endpoint ports.
portqry
-n ServerName -o 1117,1118,6001
Once you
have ran the above command the status of each of ports will be listed, either Listening, Not listening or Filtered.
If any of the ports are listed as Filtered then it fairly much rules out a
Windows and/or Exchange service issue, and is something you can take to your
Network/WAN specialists to fix for you.