MORE INFORMATION
Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
To change these parameters, use the following procedure:
- Start Registry Editor (Regedt32.exe).
- From the HKEY_LOCAL_MACHINE subtree, go to the following key:
\SYSTEM\CurrentControlSet\Services
- Add a value to the key as described in the appropriate entry below by clicking Add Value on the Edit menu, typing the value, and then using the Data Type check box to set the value type.
- Click OK.
- Quit Registry Editor.
- Reboot the computer to make the change take effect.
All of the TCP/IP parameters are registry values that are located under one of two different subkeys of
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
Tcpip\Parameters
Adapter Name\Parameters\Tcpip
where
Adapter Name refers to the subkey for a network adapter that
TCP/IP is bound to, such as Lance01. Values under the latter key(s) are specific to each adapter. Parameters for which there may be both a DHCP and statically configured value may or may not exist depending on whether the system/adapter is DHCP configured and/or static override values have been specified. A reboot of the system is required for a change in any of these parameters to take effect.
Important The Windows NT 3.5 Resource Kit documentation was not updated properly from version 3.1, and lists a number of incorrect TCP/IP registry parameters. The parameters listed in this document should be used in their place. The Windows NT 3.5 TCP/IP stack was a complete rewrite, so many of the old parameters are no longer valid.
Standard parameters configurable using Registry Editor
The following parameters are installed with default values by the Network tool in Control Panel during the installation of the TCP/IP components. They may be modified by using Registry Editor (Regedt32.exe).
DatabasePath
Key: Tcpip\Parameters
Value Type: REG_EXPAND_SZ - Character string
Valid Range: A valid Windows NT file path
Default: %SystemRoot%\system32\drivers\etc
Description: This parameter specifies the
path to the standard internet database files
(HOSTS, LMHOSTS, NETWORKS, PROTOCOLS). It is
used by the Windows Sockets interface.
ForwardBroadcasts
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: Forwarding of broadcasts is not
supported. This parameter is ignored.
UseZeroBroadcast
Key: Adapter Name\Parameters\Tcpip
In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: If this parameter is set to 1
(True), then IP will use zeros- broadcasts
(0.0.0.0) instead of ones-broadcasts
(255.255.255.255). Most systems use ones-
broadcasts, but some systems derived from BSD
implementations use zeros-broadcasts. Systems
that use different broadcasts will not
interoperate well on the same network.
Optional parameters configurable using Registry Editor
These parameters normally do not exist in the registry. They may be
created
to modify the default behavior of the TCP/IP protocol driver.
ArpAlwaysSourceRoute (new in NT 3.51)
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False or True)
Default: 0 (False)
Description: Setting this parameter to 1 will
force TCP/IP to transmit ARP queries with
source routing enabled on Token Ring
networks. By default, the stack transmits ARP
queries without source routing first and
retries with source routing enabled if no
reply was received.
ArpUseEtherSNAP
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False or True)
Default: 0 (False)
Description: Setting this parameter to 1 will
force TCP/IP to transmit Ethernet packets
using 802.3 SNAP encoding. By default, the
stack transmits packets in DIX Ethernet
format. It will always receive both formats.
DefaultTOS
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number
Valid Range: 0 - 255
Default: 0
Description: Specifies the default Type Of
Service (TOS) value set in the header of
outgoing IP packets. See RFC 791 for a
definition of the values.
Note that DefaultTOS is not available in Windows 2000 and later.
DefaultTTL
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number of
seconds/hops
Valid Range: 1-255
Default: 32 for Windows NT version 3.51
Default: 128 for Windows NT version 4.0
Description: Specifies the default Time To
Live (TTL) value set in the header of
outgoing IP packets. The TTL determines the
maximum amount of time an IP packet may live
in the network without reaching its
destination. It is effectively a limit on the
number of routers an IP packet may pass
through before being discarded.
EnableDeadGWDetect
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False, True)
Default: 1 (True)
Description: Setting this parameter to 1
causes TCP to perform Dead Gateway Detection.
With this feature enabled, TCP will ask IP to
change to a backup gateway if it retransmits
a segment several times without receiving a
response. Backup gateways may be defined in
the Advanced section of the TCP/IP
configuration dialog in the Network Control
Panel.
EnablePMTUBHDetect
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False, True)
Default: 0 (False)
Description: Setting this parameter to 1
(True) causes TCP to try to detect "Black
Hole" routers while doing Path MTU Discovery.
A "Black Hole" router does not return ICMP
Destination Unreachable messages when it
needs to fragment an IP datagram with the
Don't Fragment bit set. TCP depends on
receiving these messages to perform Path MTU
Discovery. With this feature enabled, TCP
will try to send segments without the Don't
Fragment bit set if several retransmissions
of a segment go unacknowledged. If the
segment is acknowledged as a result, the MSS
will be decreased and the Don't Fragment bit
will be set in future packets on the
connection. Enabling black hole detection
increases the maximum number of
retransmissions performed for a given
segment.
EnablePMTUDiscovery
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False, True)
Default: 1 (True)
Description: Setting this parameter to 1
(True) causes TCP to attempt to discover the
Maximum Transmission Unit (MTU or largest
packet size) over the path to a remote host.
By discovering the Path MTU and limiting TCP
segments to this size, TCP can eliminate
fragmentation at routers along the path that
connect networks with different MTUs.
Fragmentation adversely affects TCP
throughput and network congestion. Setting
this parameter to 0 causes an MTU of 576
bytes to be used for all connections that are
not to machines on the local subnet.
ForwardBufferMemory
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number of bytes
Valid Range: network MTU - some reasonable
value smaller than 0xFFFFFFFF
Default: 74240 (enough for fifty 1480-byte
packets, rounded to a multiple of 256)
Description: This parameter determines how
much memory IP allocates to store packet data
in the router packet queue. When this buffer
space is filled, the router begins discarding
packets at random from its queue. Packet
queue data buffers are 256 bytes in length,
so the value of this parameter should be a
multiple of 256. Multiple buffers are chained
together for larger packets. The IP header
for a packet is stored separately. This
parameter is ignored and no buffers are
allocated if the IP router is not enabled.
IGMPLevel
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number
Valid Range: 0,1,2
Default: 2
Description: This parameter determines to
what extent the system supports IP
multicasting and participates in the Internet
Group Management Protocol. At level 0, the
system provides no multicast support. At
level 1, the system may only send IP
multicast packets. At level 2, the system may
send IP multicast packets and fully
participate in IGMP to receive multicast
packets.
KeepAliveInterval
Key: Tcpip\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 1 - 0xFFFFFFFF
Default: 1000 (one second)
Description: This parameter determines the
interval separating keep alive
retransmissions until a response is received.
Once a response is receive, the delay until
the next keep alive transmission is again
controlled by the value of KeepAliveTime. The
connection will be aborted after the number
of retransmissions specified by
TcpMaxDataRetransmissions have gone
unanswered.
KeepAliveTime
Key: Tcpip\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 1 - 0xFFFFFFFF
Default: 7,200,000 (two hours)
Description: The parameter controls how often
TCP attempts to verify that an idle
connection is still intact by sending a keep
alive packet. If the remote system is still
reachable and functioning, it will
acknowledge the keep alive transmission. Keep
alive packets are not sent by default. This
feature may be enabled on a connection by an
application.
MTU
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD Number
Valid Range: 68 -
the MTU of the underlying
network
Default: 0xFFFFFFFF
Description: This parameter overrides the
default Maximum Transmission Unit (MTU) for a
network interface. The MTU is the maximum
packet size in bytes that the transport will
transmit over the underlying network. The
size includes the transport header. Note that
an IP datagram may span multiple packets.
Values larger than the default for the
underlying network will result in the
transport using the network default MTU.
Values smaller than 68 will result in the
tranport using an MTU of 68.
NumForwardPackets
Key: Tcpip\Parameters
Value Type: REG_DWORD Number
Valid Range: 1 - some reasonable value
smaller than 0xFFFFFFFF
Default: 50
Description: This parameter determines the
number of IP packet headers allocated for the
router packet queue. When all headers are in
use, the router will begin to discard packets
at random from the queue. This value should
be at least as large as the
ForwardBufferMemory value divided by the
maximum IP data size of the networks
connected to the router. It should be no
larger than the ForwardBufferMemory value
divided by 256, since at least 256 bytes of
forward buffer memory are used for each
packet. The optimal number of forward packets
for a given ForwardBufferMemory size depends
on the type of traffic carried on the network
and will be somewhere in between these two
values. This parameter is ignored and no
headers are allocated if the router is not
enabled.
TcpMaxConnectRetransmissions
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number
Valid Range: 0 - 0xFFFFFFFF
Default: 3 (in Windows NT)
Default: 2 (in Windows 2000)
Description: This parameter determines the
number of times TCP will retransmit a connect
request (SYN) before aborting the attempt.
The retransmission timeout is doubled with
each successive retransmission in a given
connect attempt. The initial timeout value is
three seconds.
TcpMaxDataRetransmissions
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number
Valid Range: 0 - 0xFFFFFFFF
Default: 5
Description: This parameter controls the
number of times TCP will retransmit an
individual data segment (non connect segment)
before aborting the connection. The
retransmission timeout is doubled with each
successive retransmission on a connection. It
is reset when responses resume. The base
timeout value is dynamically determined by
the measured round-trip time on the
connection.
TcpNumConnections
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number
Valid Range: 0 - 0xfffffe
Default: 0xfffffe
Description: This parameter limits the
maximum number of connections that TCP may
have open simultaneously.
TcpTimedWaitDelay (new in Windows NT versions 3.51 SP5 and later)
Key: Tcpip\Parameters
Value Type: REG_DWORD - Time in seconds
Valid Range: 30-300 (decimal)
Default: 0xF0 (240 decimal)
Description: This parameter determines the length of time that a
connection will stay in the TIME_WAIT state when being closed. While a
connection is in the TIME_WAIT state, the socket pair cannot be re-
used. This is also known as the "2MSL" state, as by RFC the value
should be twice the maximum segment lifetime on the network. See
RFC793 for further details.
TcpUseRFC1122UrgentPointer
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0,1 (False, True)
Default: 0 (False)
Description: This parameter determines
whether TCP uses the RFC 1122 specification
for urgent data or the mode used by BSD-
derived systems. The two mechanisms interpret
the urgent pointer in the TCP header and the
length of the urgent data differently. They
are not interoperable. Windows NT defaults to
BSD mode.
TcpWindowSize
Key: Tcpip\Parameters
Value Type: REG_DWORD - Number of bytes
Valid Range: 0 - 0xFFFF
Default: The smaller of 0xFFFF
OR
(The larger of four times the maximum TCP
data size on the network
OR
8192 rounded up to an even multiple of the
network TCP data size.)
The default is 8760 for Ethernet.
Description: This parameter determines the
maximum TCP receive window size offered by
the system. The receive window specifies the
number of bytes a sender may transmit without
receiving an acknowledgment. In general,
larger receive windows will improve
performance over high (delay * bandwidth )
networks. For highest efficiency, the receive
window should be an even multiple of the TCP
Maximum Segment Size (MSS).
Parameters configurable from the Network tool in Control Panel
The following parameters are created and modified automatically by the
Network tool in Control Panel
as a result of user-supplied information. There should be no need to
configure them directly in the registry.
DefaultGateway
Key: AdapterName\\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_MULTI_SZ - List of dotted
decimal IP addresses
Valid Range: Any set of valid IP addresses
Default: None
Description: This parameter specifies the
list of gateways to be used to route packets
not destined for a subnet that the computer
is directly connected to, and for which a
more specific route does not exist. This
parameter, if it has a valid value, overrides
the DhcpDefaultGateway parameter.
Domain
Key: Tcpip\Parameters
Value Type: REG_SZ - Character string
Valid Range: Any valid DNS domain name
Default: None
Description: This parameter specifies the DNS
domain name of the system. It is used by the
Windows Sockets interface.
EnableDhcp
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: If this par
ameter is set to 1
(True), then the DHCP client service will
attempt to configure the first IP interface
on the adapter using DHCP.
Hostname
Key: Tcpip\Parameters
Value Type: REG_SZ - Character string
Valid Range: Any valid DNS hostname
Default: The computername of the system
Description: This parameter specifies the DNS
hostname of the system, that will be returned
by the "hostname" command.
IPAddress
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_MULTI_SZ - List of dotted-
decimal IP addresses
Valid Range: Any set of valid IP addresses
Default: None
Description: This parameter specifies the IP
addresses of the IP interfaces to be bound to
the adapter. If the first address in the list
is 0.0.0.0, then the primary interface on the
adapter will be configured from DHCP. A
system with more than one IP interface for an
adapter is called "logically multihomed."
There must be a valid subnet mask value in
the SubnetMask parameter for each IP address
specified in this parameter.
IPEnableRouter
Key: Tcpip\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: Setting this parameter to 1
(True) causes the system to route IP packets
between the networks that it is connected to.
NameServer
Key: Tcpip\Parameters
Value Type: REG_SZ - A space delimited list
of dotted decimal IP addresses
Valid Range: Any set of valid IP address
Default: None (Blank)
Description: This parameter specifies the DNS
name servers to be queried by Windows Sockets
to resolve names.
SearchList
Key: Tcpip\Parameters
Value Type: REG_SZ - Delimited list of
DNS domain name suffixes
Valid Range: Any set of valid DNS domain name
suffixes (Space delimited for NT4 and earlier and Comma delimited for Win2000)
Valid Range: Any set of valid DNS domain name suffixes
Default: None
Description: This parameter specifies a list
of domain name suffixes to append to a name
to be resolved via the DNS if resolution of
the unadorned name fails. By default, the
value of the Domain parameter is appended
only. This parameter is used by the Windows
Sockets interface.
SubnetMask
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_MULTI_SZ - List of dotted
decimal IP addresses
Valid Range: Any set of valid IP addresses.
Default: None
Description: This parameter specifies the
subnet masks to be used with the IP
interfaces bound to the adapter. If the first
mask in the list is 0.0.0.0, then the primary
interface on the adapter will be configured
via DHCP. There must be a valid subnet mask
value in the this parameter for each IP
address specified in the IPAddress parameter.
Parameters configurable via the Route.exe command in Windows NT 3.51
In Windows NT 3.51, the route.exe command stores persistent IP routes as
values under the Tcpip\Parameters\PersistentRoutes key. Each route
is stored in the value name string as a comma-delimited list of the form:
destination,subnet mask,gateway
For example, the value representing a host route to destination
45.100.23.10 through gateway 131.110.0.1 would be named:
45.100.23.10,255.255.255.255,131.110.0.1
The value type is a REG_SZ. There is no value data (empty string).
Addition
and deletion of these values can be accomplished entirely using the
route command. There should be no need to configure them directly.
Non-configurable parameters
The following parameters are created and used internally by the TCP/IP components. They should never be modified using Registry Editor. They are listed here for reference only.
DhcpDefaultGateway
Key: Adapter Name\Parameters\ Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_MULTI_SZ - List of dotted
decimal IP addresses
Valid Range: Any set of valid IP addresses
Default: None
Description: This parameter specifies the
list of default gateways to be used to route
packets not destined for a subnet that the
computer is directly connected to, and for
which a more specific route does not exist.
This parameter is written by the DHCP client
service, if enabled. This parameter is
overridden by a valid DefaultGateway
parameter value.
DhcpIPAddress
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address
Valid Range: Any valid IP address
Default: None
Description: This parameter specifies the
DHCP-configured IP address for the interface.
If the IPAddress parameter contains a first
value other than 0.0.0.0, then that value
will override this parameter.
DhcpNameServer
Key: Tcpip\Parameters
Value Type: REG_SZ - A space delimited list
of dotted decimal IP addresses
Valid Range: Any set of valid IP address
Default: None
Description: This parameter specifies the DNS
name servers to be queried by Windows Sockets
to resolve names. It is written by the DHCP
client service, if enabled. If the NameServer
parameter has a valid value, then it will
override this parameter.
DhcpServer
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address
Valid Range: Any valid IP address
Default: None
Description: This parameter specifies the IP
address of the DHCP server that granted the
lease on the IP address in the DhcpIPAddress
parameter.
DhcpSubnetMask
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_SZ - Dotted decimal IP subnet
mask
Valid Range: Any subnet mask that is valid
for the configured IP address
Default: None
Description: This parameter specifies the
DHCP-configured subnet mask for the address
specified in the DhcpIPAddress parameter.
IPInterfaceContext
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD
Valid Range: 0 - 0xFFFFFFFF
Default: None
Description: This parameter is written by the
TCP/IP driver for use by the DHCP client
service.
Lease
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Time in seconds
Valid Range: 1 - 0xFFFFFFFF
Default: None
Description: This parameter is used by the
DHCP client service to store the time in
seconds that the lease on the IP address for
this adapter is valid for.
LeaseObtainedTime
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Absolute time in
seconds since midnight of 1/1/70
Valid Range: 1 - 0xFFFFFFFF
Default: None
Description: This parameter is used by the
DHCP client service to store the time at
which the lease on the IP address for this
adapter was obtained.
LeaseTerminatesTime
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Absolute time in
seconds since midnight of 1/1/70
Valid Range: 1 - 0xFFFFFFFF
Default: None
Description: This parameter is used by the
DHCP client service to store the time at
which the lease on the IP address for this
adapter will expire.
LLInterface
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_SZ - NT device name
Valid Range: A legal NT device name
Default: Empty string (Blank)
Description: This parameter is used to direct
IP to bind to a different link-layer protocol
than the built-in ARP module. The value of
the parameter is the name of the Windows NT
device that IP should bind to. This parameter
is in conjunction with the RAS component, for
example.
T1
Key: Adapter Name\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Absolute time in
seconds since midnight of 1/1/70
Valid Range: 1 - 0xFFFFFFFF
Default: None
Description: This parameter is used by the
DHCP client service to store the time at
which the service will first try to renew the
lease on the IP address for the adapter by
contacting the server that granted the lease.
T2
Key: AdapterName\Parameters\Tcpip
Note In Windows 2000 and later this value is under the following key:
Key: Tcpip\Parameters\Interfaces\ID for Adapter
Value Type: REG_DWORD - Absolute time in
seconds since midnight of 1/1/70
Valid Range: 1 - 0xFFFFFFFF
Default: None
Description: This parameter is used by the
DHCP client service to store the time at
which the service will try to renew the lease
on the IP address for the adapter by
broadcasting a renewal request. Time T2
should only be reached if the service has
been unable to renew the lease with the
original server for some reason.
NetBT
All of the NetBT parameters are registry values located under one of two different subkeys of
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
Netbt\Parameters
Netbt\Adapters\Adapter Name
where
Adapter Name refers the subkey for a network adapter that NetBT is
bound to, such as Lance01. Values under the latter key(s) are
specific to each adapter. If the system is configured via DHCP, then a
change in parameters will take effect if the command ipconfig /renew is
issued in a command shell. Otherwise, a reboot of the system is required
for a change in any of these parameters to take effect.
Standard parameters configurable from Registry Editor
The following parameters are installed with default values by the Network tool in Control Panel
during the installation of the TCP/IP components. They may be modified
using Registry Editor (Regedt32.exe).
BcastNameQueryCount
Key: Netbt\Parameters
Value Type: REG_DWORD - Count
Valid Range: 1 to 0xFFFF
Default: 3
Description: This value determines the number of times NetBT broadcasts a query for a given
name without receiving a response.
BcastQueryTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 100 to 0xFFFFFFFF
Default: 0x2ee ( 750 decimal)
Description: This value determines the time
interval between successive broadcast name
queries for the same name.
CacheTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 60000 to 0xFFFFFFFF
Default: 0x927c0 ( 600000 milliseconds = 10
minutes)
Description: This value determines the time
interval that names are cached in the remote
name table.
NameServerPort
Key: Netbt\Parameters
Value Type: REG_DWORD - UDP port number
Valid Range: 0 - 0xFFFF
Default: 0x89
Description: This parameter determines the
destination port number to which NetBT will
send name service related packets such as
name queries and name registrations to WINS.
The Microsoft WINS listens on port 0x89.
NetBIOS name servers from other vendors may
listen on different ports.
NameSrvQueryCount
Key: Netbt\Parameters
Value Type: REG_DWORD - Count
Valid Range: 0 - 0xFFFF
Default: 3
Description: This value determines the number
of times NetBT sends a query to a WINS server
for a given name without receiving a
response.
NameSrvQueryTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 100 - 0xFFFFFFFF
Default: 1500 (1.5 seconds)
Description: This value determines the time
interval between successive name queries to
WINS for a given name.
SessionKeepAlive
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 60,000 - 0xFFFFFFFF
Default: 3,600,000 (1 hour)
Description: This value determines the time
interval between keepalive transmissions on a
session. Setting the value to 0xFFFFFFF
disables keepalives.
Size/Small/Medium/Large
Key: Netbt\Parameters
Value Type: REG_DWORD
Valid Range: 1, 2, 3 (Small, Medium, Large)
Default: 1 (Small)
Description: This value determines the size
of the name tables used to store local and
remote names. In general, Small is adequate.
If the system is acting as a proxy
nameserver, then the value is automatically
set to Large to increase the size of the name
cache hash table. Hash table buckets are
sized as follows:
Large: 256 Medium: 128 Small: 16
Optional parameters configurable from Registry Editor
These parameters normally do not exist in the registry. They may be
created
to modify the default behavior of the NetBT protocol driver.
BroadcastAddress
Key: Netbt\Parameters
Value Type: REG_DWORD - Four byte, little-
endian encoded IP address
Valid Range: 0 - 0xFFFFFFFF
Default: The ones-broadcast address for each
network.
Description: This parameter can be used to
force NetBT to use a specific address for all
broadcast name related packets. By default,
NetBT uses the ones-broadcast address
appropriate for each net (i.e., for a network
of 11.101.0.0 with a subnet mask of
255.255.0.0, the subnet broadcast address
would be 11.101.255.255). This parameter
would be set, for example, if the network
uses the zeros-broadcast address (set using
the UseZeroBroadcast TCP/IP parameter). The
appropriate subnet broadcast address would
then be 11.101.0.0 in the example above. This
parameter would then be set to 0x0b650000.
Note that this parameter is global and will
be used on all subnets that NetBT is bound
to.
EnableProxyRegCheck
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: If this parameter is set to 1
(True), then the proxy name server will send
a negative response to a broadcast name
registration if the name is already
registered with WINS or is in the proxy's
local name cache with a different IP address.
The hazard of enabling this feature is that
it prevents a system from changing its IP
address as long as WINS has a mapping for the
name. For this reason, it is disabled by
default.
InitialRefreshTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 960000 - 0xFFFFFFF
Default: 960000 (16 minutes)
Description: This parameter specifies the
initial refresh timeout used by NetBT during
name registration. NetBT tries to contact the
WINS servers at 1/8th of this time interval
when it is first registering names. When it
receives a successful registration response,
that response will contain the new refresh
interval to use.
Note In Windows 2000, the name for this parameter differs:
InitialRefreshT.O.
Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NetBT\Parameters
LmhostsTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 1000 - 0xFFFFFFFF
Default: 6000 (6 seconds)
Description: This parameter specifies the
timeout value for Lmhosts and DNS name
queries. The timer has a granularity of the
timeout value, so the actual timeout could be
as much as twice the value.
MaxDgramBuffering
Key: Netbt\Parameters
Value Type: REG_DWORD - Count of bytes
Valid Range: 0 - 0xFFFFFFFF
Default: 0x20000 (128 Kb)
Description: This parameter specifies the
maximum amount of memory that NetBT will
dynamically allocate for all outstanding
datagram sends. Once this limit is reached,
further sends will fail due to insufficient
resources.
NodeType
Key: Netbt\Parameters
Value Type: REG_DWORD - Number
Valid Range: 1,2,4,8 (B-node, P-node, M-node,
H-node)
Default: 1 or 8 based on the WINS server
configuration
Description: This parameter determines what
methods NetBT will use to register and
resolve names. A B-node system uses
broadcasts. A P-node system uses only point-
to-point name queries to a name server
(WINS). An M-node system broadcasts first,
then queries the name server. An H-node
system queries the name server first, then
broadcasts. Resolution via LMHOSTS and/or
DNS, if enabled, will follow the these
methods. If this key is present it will
override the DhcpNodeType key. If neither key
is present, the system defaults to Bnode if
there are no WINS servers configured for the
network. The system defaults to Hnode if
there is at least one WINS server configured.
RandomAdapter
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: This parameter applies to a
multihomed host only. If it is set to 1
(True), then NetBT will randomly choose the
IP address to put in a name query response
from all of its bound interfaces. Usually,
the response contains the address of the
interface that the query arrived on. This
feature would be used by a server with two
interfaces on the same network for load
balancing.
RefreshOpCode
Key: Netbt\Parameters
Value Type: REG_DWORD - Number
Valid Range: 8, 9
Default: 8
Description: This parameter forces NetBT to
use a specific opcode in name refresh
packets. The specification for the NetBT
protocol is somewhat ambiguous in this area.
Although the default of 8 used by Microsoft
implementations appears to be the intended
value, some other implementations, such as
those by Ungermann-Bass, use the value 9. Two
implementations must use the same opcode to
interoperate.
SingleResponse
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: This parameter applies to a
multihomed host only. If this parameter is
set to 1 (True), then NetBT will only supply an
IP address from one of its bound interfaces
in name query responses. By default, the
addresses of all bound interfaces are
included.
WinsDownTimeout
Key: Netbt\Parameters
Value Type: REG_DWORD - Time in milliseconds
Valid Range: 1000 - 0xFFFFFFFF
Default: 15,000 ( 15 seconds)
Description: This parameter determines the
amount of time NetBT will wait before again
trying to use WINS after it fails to contact
any WINS server. This feature primarily
allows computers that are temporarily
disconnected from the network, such as
laptops, to proceed through boot processing
without waiting to timeout out each WINS name
registration or query individually.
Parameters configurable from the Network tool in Control Panel
The following parameters can be set via the Network tool in Control Panel. There should be no need
to configure them directly.
EnableDns
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: If this value is set to 1
(True), then NetBT will query the DNS for names
that cannot be resolved by WINS, broadcast,
or the LMHOSTS file.
EnableLmhosts
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 1 (True)
Description: If this value is set to 1
(True), then NetBT will search the LMHOSTS
file, if it exists, for names that cannot be
resolved by WINS or broadcast. By default
there is no Lmhosts file database directory
(specified by Tcpip\Parameters\DatabasePath),
so no action will be taken. This value is
written by the Advanced TCP/IP configuration
dialog of the Network tool in Control Panel.
EnableProxy
Key: Netbt\Parameters
Value Type: REG_DWORD - Boolean
Valid Range: 0 or 1 (False or True)
Default: 0 (False)
Description: If this value is set to 1
(True), then the system will act as a proxy
name server for the networks that NetBT is
bound to. A proxy name server answers
broadcast queries for names that it has
resolved through WINS. A proxy nameserver
allows a network of Bnode implementations to
connect to servers on other subnets that are
registered with WINS.
NameServer
Key: Netbt\Adapters\Adapter Name
Note In Windows 2000 this value is under the following key:
Key: Netbt\Parameters\Interfaces\Tcpip_ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address (i.e. 11.101.1.200)
Valid Range: Any valid IP address
Default: blank ( no address )
Description: This parameter specifies the IP
address of the primary WINS server. If this
parameter contains a valid value, it
overrides the DHCP parameter of the same
name.
NameServerBackup
Key: Netbt\Adapters\Adapter Name
Note In Windows 2000 this value is under the following key:
Key: Netbt\Parameters\Interfaces\Tcpip_ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address (i.e. 11.101.1.200)
Valid Range: Any valid IP address.
Default: blank ( no address )
Description: This parameter specifies the IP
address of the backup WINS server. If this
parameter contains a valid value, it
overrides the DHCP parameter of the same
name.
ScopeId
Key: Netbt\Parameters
Value Type: REG_SZ - Character string
Valid Range: Any valid DNS domain name
consisting of two dot-separated parts, or a
"*".
Default: None
Description: This parameter specifies the
NetBIOS name scope for the node. This value
must not begin with a period. If this
parameter contains a valid value, it will
override the DHCP parameter of the same name.
A blank value (empty string) will be ignored.
Setting this parameter to the value "*"
indicates a null scope and will override the
DHCP parameter.
Non-configurable parameters
The following parameters are created and used internally by the NetBT
components. They should never be modified using Registry Editor. They
are listed here for reference only.
DhcpNameServer
Key: Netbt\Adapters\Adapter Name
Note In Windows 2000 this value is under the following key:
Key: Netbt\Parameters\Interfaces\Tcpip_ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address (i.e. 11.101.1.200)
Valid Range: Any valid IP address
Default: None
Description: This parameter specifies the IP
address of the primary WINS server. It is
written by the DHCP client service, if
enabled. A valid NameServer value will
override this parameter.
DhcpNameServerBackup
Key: Netbt\Adapters\Adapter Name
Note In Windows 2000 this value is under the following key:
Key: Netbt\Parameters\Interfaces\Tcpip_ID for Adapter
Value Type: REG_SZ - Dotted decimal IP
address (i.e. 11.101.1.200)
Valid Range: Any valid IP address
Default: None
Description: This parameter specifies the IP
address of the backup WINS server. It is
written by the DHCP client service, if
enabled. A valid BackupNameServer value will
override this parameter.
DhcpNodeType
Key: Netbt\Parameters
Value Type: REG_DWORD - Number
Valid Range: 1 - 8
Default: 1
Description: This parameter specifies the NetBT
node type. It is written by the DHCP client
service, if enabled. A valid NodeType value
will override this parameter. See the entry
for NodeType for a complete description.
DhcpScopeId
Key: Netbt\Parameters
Value Type: REG_SZ - Character string
Valid Range: a dot separated name string such
as "microsoft.com"
Default: None
Description: This parameter specifies the
NetBIOS name scope for the node. It is
written by the DHCP client service, if
enabled. This value must not begin with a
period. See the entry for ScopeId for more
information.
NbProvider
Key: Netbt\Parameters
Value Type: REG_SZ - Character string
Valid Range: _tcp
Default: _tcp
Description: This parameter is used
internally by the RPC component. The default
value should not be changed.
TransportBindName
Key: Netbt\Parameters
Value Type: REG_SZ - Character string
Valid Range: N/A
Default: \Device\
Description: This parameter is used
internally during product development. The
default value should not be changed.