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Module 9: Creating
and Managing
Routing Groups in
Exchange 2000 Information in this document is subject to change without notice. The names of companies,
products, people, characters, and/or data mentioned herein are fictitious and are in no way intended
to represent any real individual, company, product, or event, unless otherwise noted. Complying
with all applicable copyright laws is the responsibility of the user. No part of this document may
be reproduced or transmitted in any form or by any means, electronic or mechanical, for any
purpose, without the express written permission of Microsoft Corporation. If, however, your only
means of access is electronic, permission to print one copy is hereby granted.


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Lead Product Manager:
David Bramble

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To teach this module, you need the following materials:
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Microsoft PowerPoint
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file 1569A_09.ppt

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To prepare for this module, you should:
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Read all of the materials for this module.
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Complete the lab.
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Practice your demonstration.

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This section provides lab tips for labs in this module.
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During this lab, problems with Exchange 2000 Beta 3 may cause messages to
become stuck in the Simple Mail Transfer Protocol (SMTP) PreRoutingQueue

Explain how messages are transferred from sender to recipient for a variety
of scenarios. Present each slide, keeping the focus on that specific scenario,
rather than using one slide to explain every scenario.
„#
Designing Routing Groups
Discuss routing group designs, including what servers can be part of a
routing group, when to use multiple routing groups, and how to choose a
connector.
„#
Creating Routing Groups and Routing Group Connectors
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Link State
Table
Connector
Routing Group A
Routing Group A
Routing Group B
Routing Group BThe routing process for a message begins when Microsoft
®
Exchange 2000
receives a message either from a user, another computer running Exchange, or a
foreign messaging system through a connector or gateway. The server running
Exchange 2000 looks up the recipient in Active Directory™ directory service
and routes the message to the recipient.
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Previous versions of Exchange use sites to organize servers for both
communications and administration. Network bandwidth is the primary factor
in determining site boundaries. That is, network bandwidth should be high
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Routing groups are connected using connectors. Following is a list of
connectors available with Exchange 2000 that can connect routing groups
together:
„#
Routing group connector
„#
Simple Mail Transfer Protocol connector
„#
X.400 connector

Connectors designed for third party mail systems cannot be used to connect
routing groups.
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The Exchange 2000 routing and selection process uses a link state table to
determine the shortest path between two routing groups for a given message. To
provide an efficient fault tolerant routing mechanism, Exchange 2000 uses a
link state table. The link state table is stored on each server running
Exchange 2000 and contains the status of each connector in the Exchange 2000
organization. If a server running Exchange 2000 cannot find a route for a
particular message after referring to the link state table, it will not attempt to
deliver the message.
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0XVW#EH#DEOH#WR#FRQQHFW#WR#URXWLQJ#JURXS#PDVWHUServers within a single routing group must have permanent connectivity
between them. Messages are delivered in a single hop, immediately, with no
scheduling of message delivery.
Servers within a routing group communicate directly to each other. The
following must apply to servers within the same routing group:
„#
Servers running Exchange must belong to the same Active Directory forest.
„#

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conditions:
„#
Network connectivity is unreliable.
•
Network traffic is saturated to the point that communications are not
reliable.
•
The underlying network experiences frequent problems.
„#
You want to control the message paths within an Exchange organization.
For example, the messaging path needs to be altered from single-hop to
multi-hop, such as when servers are located in separate physical locations,
but communicate in a single-hop environment.
„#
You want to schedule messaging between two locations.

If you have a single physical location and all servers are connected through a
reliable, permanent link, you may not require multiple routing groups.
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only a single connector between the hub and each spoke. With Exchange 2000
and the link state table, this topology is not necessary because messages are not
bounced back and forth. If a connector fails, the message may be rerouted
through another routing group, but will not bounce back to the original routing
group.
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Message traffic analysis can provide helpful information regarding which
servers communicate with each other the most. It can be efficient to include
servers that communicate regularly in the same routing group. However,
designing routing groups solely based on traffic analysis, without regard to
management overhead, may not be the most efficient solution.
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Some additional considerations may impact how you design a routing group.
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Servers can be connected over slow (but reliable) links as part of the same
routing group.
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Routing groups are dynamic, and they can be changed at any time.
„#
The routing group architecture determines public folder access.

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SMTP connector
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X.400 connector

The Routing Group Connector can only connect routing groups. Other
connectors provide connections to foreign systems in addition to connecting
routing groups within an organization.
When you configure a connector on a server, the connector is included in the
routing process for messages destined outside of the routing group. Servers
running Exchange 2000 that host routing group connectors are called
bridgehead servers. All messages that are delivered between routing groups
pass through the bridgehead server that hosts the routing group connector.
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multiple servers identified as bridgehead servers for a routing group connector
is that if a bridgehead server is down, Exchange can choose another bridgehead
server within the routing group to transmit the message.
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Exchange 2000 provides SMTP authentication between bridgehead servers.
Encryption of messages between bridgehead servers is not enabled by default.
If encryption is required, you can implement IPSec, which is a standard
encryption method for Transmission Control Protocol/Internet Protocol
(TCP/IP) network security. IPSec is available with Windows 2000. However,
messages transferred between servers running Exchange 2000 are in Transport-
Neutral Encapsulation Format (TNEF), and not in plain text.
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When the bridgehead server that hosts the Routing Group Connector receives a
message to be delivered across the connector, the bridgehead server tries to
resolve the target server’s Internet Protocol (IP) address by using the standard
SMTP resolution process. That is, the bridgehead server first tries to resolve the
target server defined on the Routing Group Connector by using Domain Name
System (DNS) mail exchange (MX) records. If no MX records exist for the

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SMTP
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Bridgehead
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Bridgehead
Server
Bridgehead
ServerSMTP connectors can be used to connect routing groups. They should be used
when:
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The other side of the connector is the Internet Mail Service (IMS) from
previous versions of Exchange.
„#
When a pull-relationship is required between servers. Where one side
queues messages and the other side pulls them by using the TRN or ETRN
command.
„#
When you want to define Secure Sockets Layer (SSL) or other security
parameters.

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Each SMTP connector can specify multiple bridgehead servers within each
routing group. All messages from the bridgehead servers to the target routing
group will either be delivered directly after MX resolution by DNS or

When multiple target servers exist for an SMTP connector, Exchange 2000
code intercepts the request, looks up the target servers, and returns them to
SMTP before SMTP resolves the MX record against a DNS server.
With an SMTP connector, you can optimize the message transport to a greater
extent than with a Routing Group Connector. SMTP connector options include
authenticating remote domains before sending mail, designating specific times
when mail can be sent, and setting multiple permission levels for multiple users
on the connector.
When creating an SMTP connector, there are three important considerations.
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A smart host is an intermediary host that uses DNS to resolve the destination
host’s IP address and then sends the message to the destination host. The smart
host server must be able to process mail for the remote address space or routing
group that the SMTP connector needs to reach. The SMTP connector relays all
messages through the smart host, which passes them on to the remote
destination by using DNS.
A smart host is helpful for messages traveling between servers over the
Internet, such as when the remote domain can only be reached during certain
times or infrequently. Instead of repeatedly contacting the domain until a
connection is made, the server running Exchange only needs to transmit to the
smart host. Then the smart host makes the remote connection.
If a smart host is not designated, a DNS lookup will be made on every address
to which the SMTP connector sends e-mail.

If you use an IP address to identify the smart host, enclose the address in
brackets ([ ]) to increase system performance. The SMTP service first checks
for a server name, then an IP address. The brackets identify the value as an IP
address, so that the DNS lookup is bypassed.

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Use the X.400 connector to connect routing groups in the following situations:
„#
When the network connection between routing groups is X.25.
„#
When the network connection between routing groups is over Remote
Access Service (RAS).

You can configure multiple X.400 connectors, each using different transport
stacks, such as X.25, Transport Control Protocol (TCP), or remote access
functionality. To connect two routing groups, you must configure X.400
connectors in both routing groups to create a two-way connection.
To provide load balancing and fault tolerance between two routing groups with
the X.400 connector you need to configure multiple connectors.
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If Exchange 2000 does not provide a connector for a non-Exchange
system, such as Profs, but such a connector is offered by a legacy Exchange
system, you can use that connector by establishing a legacy Exchange site that
hosts the connector in the Exchange 2000 organization.

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JURXSVExchange 2000 builds upon the routing architecture in previous versions of
Exchange Server where the available routes and costs in the organization are
available to any messaging server. The link state table replaces the gateway
address resolution table and adds additional functionality.
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There are only two states for any given link: UP or DOWN; so connection
information, such as whether a link is active or in a retry state, is not propagated
and is only known on the server involved in the message transfer.
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The administrator designates a server to be the routing group master for a
routing group. The routing group master maintains link state information
received from different sources. The routing group master tracks this data and
propagates it to the rest of the servers within the routing group. The first server
added to a routing group becomes the routing group master, but this can be
changed through the Exchange System Manager console.
If the routing group master fails, an administrator must designate a new routing
group master. The servers running Exchange 2000 in the routing group will
continue to use the existing link state table, without updates, until the original
routing group master returns or a new routing group master is designated.

The status of connectors can be viewed from the Exchange System
Manager, under Tools, Monitors.

so that messages are not sent along a path where a link may have failed.
„#
The link state algorithm eliminates message bounce between servers,
because each server running Exchange 2000 knows whether other alternate
or redundant links are UP or DOWN.
„#
The link state algorithm overcomes message ping-pong problems.

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