Q129005: Sockets Applications Do Not Switch to Second NIC if One
Article: Q129005
Product(s): Microsoft Windows NT
Version(s):
Operating System(s):
Keyword(s):
Last Modified: 08-AUG-2001
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The information in this article applies to:
- Microsoft Windows NT Server version 3.1
- Microsoft Windows NT Workstation version 3.1
- Microsoft Windows NT Advanced Server, version 3.1
- Microsoft Windows NT Workstation version 3.5
- Microsoft Windows NT Server version 3.5
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SUMMARY
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If a computer running Windows NT has multiple network adapters, each connected
to the same physical subnet through additional hardware (such as a switch),
sockets applications use only one of the adapters to communicate over the
network. In addition, if the intermediate hardware fails, sockets applications
do not detect the failure and do not attempt to recover by using another
adapter/switch combination.
MORE INFORMATION
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You can use network hardware in parallel configurations to provide fault
tolerance. For example, you can put two network adapters in the same computer,
connected to the same physical subnet, so that if one adapter fails the other
can take over. If you need intermediate hardware, such as a switch, to connect
each adapter to the network, you can attach one switch to each adapter, rather
than connecting all the adapters to the same switch.
This strategy assumes that the applications communicating over the network can
detect the failure of one set of network hardware and automatically start using
the other one. Unfortunately, many sockets applications do not detect hardware
failure, and will not automatically use the other set of hardware. For example,
you run the LPR print monitor on a Windows NT print server with two network
adapters, each with its own switch. When LPR initializes, it makes sockets calls
that complete correctly as long as one of the network adapters is functioning,
even if the switch connecting that adapter to the network has failed. LPR has no
way to determine if the failure is with the switch, rather than with other
hardware on the network. Therefore, LPR has no reason to try the other
adapter/switch combination. While LPR is running it can tell when it loses
connections with LPD servers, but it does not know why. If also doesn't know to
try using another adapter to work around the problem.
NOTE: This problem applies to hardware connecting the computer to the network,
not to other devices on the network, such as routers. For example, if there are
multiple routes from the Windows NT LPR client to an LPD server, and one route
fails, TCP/IP will automatically use a different route, and LPR will continue
sending its print jobs.
Additional query words: 3.10 prodnt
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Keywords :
Technology : kbWinNTsearch kbWinNTWsearch kbWinNT350search kbWinNTW350 kbWinNTW350search kbWinNTW310 kbWinNTSsearch kbWinNTS350 kbWinNTS310 kbWinNTAdvSerSearch kbWinNTAdvServ310 kbWinNTS350search kbWinNTS310search kbWinNT310Search kbWinNTW310Search
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