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EnableAddrMaskReply

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Data type

Range

Default value

REG_DWORD

0 | 1

0

Description

Determines whether the computer responds to Internet Control Message Protocol (ICMP) address mask requests by sending ICMP address mask replies.

ICMP is an error-reporting and diagnostic utility in IP. Routers, intermediary devices, and hosts use ICMP messages to communicate with each other.

An address mask request (ICMP Type 17) is an ICMP message that a networked computer issues to determine the subnet mask on the local network. RFC 1122, Requirements for Internet hosts—communication layers, restricts the computers that can respond to address mask requests to authoritative agents (hosts or gateways) that are explicitly configured to respond to address masks.

If the computer responds to address mask requests, malicious users might be able to discover sections of the network topology.

Value

Meaning

0

Disabled. The system does not reply to address mask requests.

1

Enabled. The system responds to address mask requests by sending address mask replies (ICMP Type 18).

Note Image Note

Windows 2000 does not add this entry to the registry. You can add it by editing the registry or by using a program that edits the registry.

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