Several network adapters


G

Guest

What rules are there that decides which network adapter (assuming I have
several network adapters on my PC) network information uses to send
information on a Windows XP Pro PC?
 
S

Steve Winograd [MVP]

What rules are there that decides which network adapter (assuming I have
several network adapters on my PC) network information uses to send
information on a Windows XP Pro PC?
I assume that the computer uses the TCP/IP protocol on the network.

Windows XP creates a network connection for each installed network
adapter. It decides which connection to use by looking up the
destination IP address in the TCP/IP route table, which defines the
range of IP addresses that each connection can access.

When multiple connections can access the same destination, XP uses the
connection with the lowest metric value. By default, XP assigns a
metric value based on the rated speed of a connection:

An explanation of the Automatic Metric feature for Internet Protocol
routes
http://support.microsoft.com/Default.aspx?id=299540

If automatic metrics don't do what you want, you can assign them
manually. To assign a metric to a network connection:

1. Open the Network Connections folder.
2. Right click the desired connection.
3. Click Properties | Internet Protocol (TCP/IP).
4. Click Properties | Advanced.
5. Un-check "Automatic metric".
6. Enter a number between 1 and 9999 for the "Interface metric".
--
Best Wishes,
Steve Winograd, MS-MVP (Windows Networking)

Please post any reply as a follow-up message in the news group
for everyone to see. I'm sorry, but I don't answer questions
addressed directly to me in E-mail or news groups.

Microsoft Most Valuable Professional Program
http://mvp.support.microsoft.com
 
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G

Guest

On the local network the binding-order determines this.

Over longer distances the number of 'hops' (routing cost) for each route may
come into play.
 
S

Steve Winograd [MVP]

Ian said:
On the local network the binding-order determines this.
What do you mean by "binding-order", Ian, and how do you configure it?

If you mean the order in which connections appear in the Connections
window of Network Connections > Advanced > Advanced Settings >
Adapters and Bindings, then I disagree. If you mean something else,
please describe it.

For the TCP/IP protocol, Windows XP looks at the route table to
determine which connection(s) can reach a destination IP address.
When more than one connection is possible, XP looks at the metrics for
the connections and uses the one with the lower metric. Even if the
metrics are equal, the binding order has no effect on LAN use in my
tests, both for pings and for accessing shared folders.

This behavior is the same for all networks. Windows XP doesn't
distinguish between LANs, WANs, etc.
Over longer distances the number of 'hops' (routing cost) for each route may
come into play.
I don't know of any way that Windows XP computes or uses the number of
'hops' to a destination. If you do, please describe it. Routing
choices are based on metrics. XP computes metrics based on connection
speeds.
--
Best Wishes,
Steve Winograd, MS-MVP (Windows Networking)

Please post any reply as a follow-up message in the news group
for everyone to see. I'm sorry, but I don't answer questions
addressed directly to me in E-mail or news groups.

Microsoft Most Valuable Professional Program
http://mvp.support.microsoft.com
 
G

Guest

Thank you Steve,

Lets say I set a lower metric on one adapter and a higher one on another.
Will then an application try the adapter with the higher metric if it cannot
find a host using the adapter with the lower metric?

Best Regards,
Joachim
 
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S

Steve Winograd [MVP]

Thank you Steve,

Lets say I set a lower metric on one adapter and a higher one on another.
Will then an application try the adapter with the higher metric if it cannot
find a host using the adapter with the lower metric?
No, it won't. If the adapter with the lower metric can't contact the
host, the connection attempt will fail.

If you always want to use a specific adapter to contact a specific
host, you can specify a persistent route to that host. For example,
if the host's address is 192.168.123.100 and the desired adapter is
192.168.123.2:

route -p add 192.168.123.100 mask 255.255.255.255 192.168.123.2
Best Regards,
Joachim
You're welcome, Joachim.
--
Best Wishes,
Steve Winograd, MS-MVP (Windows Networking)

Please post any reply as a follow-up message in the news group
for everyone to see. I'm sorry, but I don't answer questions
addressed directly to me in E-mail or news groups.

Microsoft Most Valuable Professional Program
http://mvp.support.microsoft.com
 

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