MORE INFORMATION
Connecting a computer to a remote network through a dial-up
or Virtual Private Networking (VPN) connection changes the routing table which
controls the flow of packets. After this connection has been established,
Microsoft remote access clients create a new default route pointing to the new
connection. As a result, when a computer that is connected to one network
establishes a new connection to another network, any packet which is not
addressed to the immediate subnet will be routed through the dial-up
connection.
One common situation where this behavior is encountered
is during VPN connections across the Internet to a corporate network. When this
connection is made, all connections to the Internet (for example, Microsoft
Internet Explorer connections) are not possible without manual modifications to
the routing table.
Connection Manager enables the deployment of such
route table modifications through the use of a CmRoute connection action. This
action uses the information associated with the default route entry in the
routing table to identify the user interface associated with the new
connection. CmRoute uses this information to create a new set of routes based
on the routing table entries provided by a network administrator.
With CmRoute, there are two ways for the routing information to be specified:
- Static routes can be supplied in a routing file located on
the user's computer. This file is prepared by the network administrator as part
of the Connection Manager profile.
- Additional routes can be downloaded from a remote server at
a predetermined Uniform Resource Locator (URL) location each time the client is
connected. The additional route table (if any) is processed after the static
route table (if any). Because the route file syntax supports both add and delete commands, these additional routes can either add to or replace
entries that are defined in the Static Routes file.
The
Routing Table Update dialog box, in CMAK, enables you to use the CmRoute connect
action and a path to the route table which is distributed in the Connection
Manager profile. This file contains the route entry modifications to be made to
the client.
A Syntax of the Route Table
The Routing Table Update files are plain-text files that you can
create and edit in any plain-text editor, such as, Microsoft Windows Notepad.
The syntax of the entries in the table is based on the
command destination mask netmask gateway metric metric
command.
In addition, where "default" is used in an entry, CmRoute
can substitute the corresponding value obtained from the default route
entry.
A route entry example:
add 192.168.1.0 mask
255.255.255.0 default metric default if default
An Example of Route Table Changes
Before the Connection Manager Connection Is Made:
This is the normal route table before any changes are made:
Windows IP Configuration
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 10.1.1.2
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.1.1.3
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 c0 4f 86 d8 72 ...... 3Com 3C905TX-based Ethernet Adapter (Generic
===========================================================================
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.1.1.3 10.1.1.2 1
10.1.1.0 255.255.255.0 10.1.1.2 10.1.1.2 1
10.1.1.2 255.255.255.255 127.0.0.1 127.0.0.1 1
10.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
224.0.0.0 240.0.0.0 10.1.1.2 10.1.1.2 1
255.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
Default Gateway: 10.1.1.3
===========================================================================
Persistent Routes:
None
After the Connection Manager Connection Is Made:
This example is after the Connection Manager connection is made
(with the
Use Default Gateway on Remote Network option
enabled), but before CmRoute begins (the step where CmRoute obtains the gateway
information):
Windows IP Configuration
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 10.1.1.2
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.1.1.3
PPP adapter Virtual Private Connection:
Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 6.6.6.7
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . : 6.6.6.7
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 c0 4f 86 d8 72 ...... 3Com 3C905TX-based Ethernet Adapter (Generic
0x100004 ...00 53 45 00 00 00 ...... WAN (PPP/SLIP) Interface
===========================================================================
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 6.6.6.7 6.6.6.7 1
0.0.0.0 0.0.0.0 10.1.1.3 10.1.1.2 2
6.6.6.7 255.255.255.255 127.0.0.1 127.0.0.1 1
6.255.255.255 255.255.255.255 6.6.6.7 6.6.6.7 1
10.1.1.0 255.255.255.0 10.1.1.2 10.1.1.2 1
10.1.1.2 255.255.255.255 127.0.0.1 127.0.0.1 1
10.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
224.0.0.0 240.0.0.0 6.6.6.7 6.6.6.7 1
224.0.0.0 240.0.0.0 10.1.1.2 10.1.1.2 1
255.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
Default Gateway: 6.6.6.7
===========================================================================
Persistent Routes:
None
After CmRoute Has Run:
This example assumes that the following
route add statement is in the CmRoute file:
add 192.168.1.0 mask 255.255.255.0 default metric default if default
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...00 c0 4f 86 d8 72 ...... 3Com 3C905TX-based Ethernet Adapter (Generic
0x100004 ...00 53 45 00 00 00 ...... WAN (PPP/SLIP) Interface
===========================================================================
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 6.6.6.7 6.6.6.7 1
0.0.0.0 0.0.0.0 10.1.1.3 10.1.1.2 2
6.6.6.7 255.255.255.255 127.0.0.1 127.0.0.1 1
6.255.255.255 255.255.255.255 6.6.6.7 6.6.6.7 1
10.1.1.0 255.255.255.0 10.1.1.2 10.1.1.2 1
10.1.1.2 255.255.255.255 127.0.0.1 127.0.0.1 1
10.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
192.168.1.0 255.255.255.0 6.6.6.7 6.6.6.7 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
224.0.0.0 240.0.0.0 6.6.6.7 6.6.6.7 1
224.0.0.0 240.0.0.0 10.1.1.2 10.1.1.2 1
255.255.255.255 255.255.255.255 10.1.1.2 10.1.1.2 1
Default Gateway: 6.6.6.7
===========================================================================
Persistent Routes:
None