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Technical User
The scope of IP address ranges (and exclusions) are specified using the DHCP console. To define IP scope options and client reservations: invoke DHCP from Administrative Tools or use the netsh dial-up scripting utility on the three sub-contexts: interface, ras, routing. Static IP Addresses used for servers on the network should be specified in DHCP Exclusion scopes. A Superscope combines individual scopes (within a single physical segment) into a logical multinet. Superscopes are used when several DHCP servers serve a single subnet. (In Windows 2000, they can only be specified after a scope has been defined) To ensure that individual DHCP clients always receive addresses from the same DHCP server, create on each DHCP server the same superscope with a member scope for the IP range managed by each DHCP server. This is so DHCP servers do not send DHCPNak messages for ranges of other DHCP servers. Then on each DHCP server exclude ranges for other servers.
Multicasting
MADCAP (Multicast Address Client Allocation Protocol) is used to multicast to IPv4 Class D addresses. Use the 239.x.x.x range and avoid 224-238 to prevent multicast traffic from being copied to the adjoining host. Activating the scope is a separate manual step commonly missed.
DHCP Lease durations are changed in Scope properties. The default is 3 days in Windows NT and 8 days in Windows 2000. By default, the dynamic update client dynamically registers A and PTR resource records: Every 24 hours Its TCP/IP configuration is changed Its DHCP address is renewed or new lease obtained A Plug and Play event occurs Some DHCP clients cannot perform dynamic updates. Client OS Command
Windows 2000 ipconfig /registerdns
Windows NT 4 ipconfig /release ipconfig /renew
Windows 9x winipcfg /renew
Commands to force re-registration of IP addresses differ by OS: The client broadcasts a DHCPREQUEST to attempt to renew its lease at 50% (point T1) and at 87.5% (point T2). By default, DHCP servers are set to “Automatically update DHCP client information in DNS” — A and PTR records.
DHCP Advanced User Classes
A convenient way to specify one set of DHCP configuration settings for a group ofDHCP clients (such as short lease period for mobile DHCP clients who typically log in for only a few hours at a time), from the DHCP console tree, choose from the context menu "Define User Class" and click Add. Specify the class name and description. Then configure advanced options for the user class. To invoke DHCP class id XXXX on each DHCP client computer: ipconfig /setclassid xxxx
DHCP Logging
HKLM\ SYSTEM\ CurrentControlSet\ Services\ DhcpServer\ Parameters\
Key Data Type Default Value
ActivityLogFlag REG_DWORD 1
DhcpLogFilePath REG_SZ System32\dhcp
DhcpLogMinSpaceOnDisk REG_DWORD 20mb
DhcpLogDiskSpaceCheckInterval REG_DWORD 50mb
DhcpLogFilesMaxSize REG_DWORD 7mb
Network Address Translation
NAT provides IP address assignment and DNS Proxy name resolution services to internal network clients. NAT is emphasized over ICS because NAT provides a higher level of customization and control. A NAT server allows outbound traffic to the external internet. By default, a NAT server allows inbound traffic only through connections already established by an internet host (typically port 80). To access traffic from a special port from an external host: If the public interface of the NAT server is configured with a single IP address, add a Special Port in the Routing and Remote Assess MMC console. If the public interface of the NAT server is configured with multiple IP addresses, make address reservations to map specific external addresses to specific internal addresses. Selection of 006 DNS Servers option at the scope level overrides the selection at the server level.
Internet Connection Sharing (ICS) using 192.168ICS is used in small offices to do the work of a DNS server for name resolution, and DHCP servers for automatic Internet Protocol (IP) address allocation. In other words, ICS can NOT be used on a network with DNS and DHCP servers. After ICS is enabled, no further configuration of DNS or IP addressing services can be allowed on the network. ICS provides a proxy server service and Internet gateway. ICS and Windows 2000 routes packets from the internal LAN through one NIC on the internal subnet and out another NIC facing the external internet. ICS allows clients to use standard Internet tools to access e-mail or the Web, or perform any other operations supported by the Internet. ICS is implemented by setting the TCP/IP connection property. During ICS installation, the ICS DHCP allocator is automatically enabled. Windows 2000 Server uses the ICS DHCP allocator (a simplified DHCP process) to automatically assign clients private IP addresses in the range of 192.168.0.2 to 192.168.254.254 and a class C subnet mask of 255.255.255.0. The server’s NIC which connects to the internal LAN is assigned the “LINKLOCAL Network” static private IP address of 192.168.0.1. This is the IP gateway address for other clients on the LAN. The external NIC can include a standard telephone modem. If so, check the “Enable On-Demand Dialing” option.
Multicasting
MADCAP (Multicast Address Client Allocation Protocol) is used to multicast to IPv4 Class D addresses. Use the 239.x.x.x range and avoid 224-238 to prevent multicast traffic from being copied to the adjoining host. Activating the scope is a separate manual step commonly missed.
DHCP Lease durations are changed in Scope properties. The default is 3 days in Windows NT and 8 days in Windows 2000. By default, the dynamic update client dynamically registers A and PTR resource records: Every 24 hours Its TCP/IP configuration is changed Its DHCP address is renewed or new lease obtained A Plug and Play event occurs Some DHCP clients cannot perform dynamic updates. Client OS Command
Windows 2000 ipconfig /registerdns
Windows NT 4 ipconfig /release ipconfig /renew
Windows 9x winipcfg /renew
Commands to force re-registration of IP addresses differ by OS: The client broadcasts a DHCPREQUEST to attempt to renew its lease at 50% (point T1) and at 87.5% (point T2). By default, DHCP servers are set to “Automatically update DHCP client information in DNS” — A and PTR records.
DHCP Advanced User Classes
A convenient way to specify one set of DHCP configuration settings for a group ofDHCP clients (such as short lease period for mobile DHCP clients who typically log in for only a few hours at a time), from the DHCP console tree, choose from the context menu "Define User Class" and click Add. Specify the class name and description. Then configure advanced options for the user class. To invoke DHCP class id XXXX on each DHCP client computer: ipconfig /setclassid xxxx
DHCP Logging
HKLM\ SYSTEM\ CurrentControlSet\ Services\ DhcpServer\ Parameters\
Key Data Type Default Value
ActivityLogFlag REG_DWORD 1
DhcpLogFilePath REG_SZ System32\dhcp
DhcpLogMinSpaceOnDisk REG_DWORD 20mb
DhcpLogDiskSpaceCheckInterval REG_DWORD 50mb
DhcpLogFilesMaxSize REG_DWORD 7mb
Network Address Translation
NAT provides IP address assignment and DNS Proxy name resolution services to internal network clients. NAT is emphasized over ICS because NAT provides a higher level of customization and control. A NAT server allows outbound traffic to the external internet. By default, a NAT server allows inbound traffic only through connections already established by an internet host (typically port 80). To access traffic from a special port from an external host: If the public interface of the NAT server is configured with a single IP address, add a Special Port in the Routing and Remote Assess MMC console. If the public interface of the NAT server is configured with multiple IP addresses, make address reservations to map specific external addresses to specific internal addresses. Selection of 006 DNS Servers option at the scope level overrides the selection at the server level.
Internet Connection Sharing (ICS) using 192.168ICS is used in small offices to do the work of a DNS server for name resolution, and DHCP servers for automatic Internet Protocol (IP) address allocation. In other words, ICS can NOT be used on a network with DNS and DHCP servers. After ICS is enabled, no further configuration of DNS or IP addressing services can be allowed on the network. ICS provides a proxy server service and Internet gateway. ICS and Windows 2000 routes packets from the internal LAN through one NIC on the internal subnet and out another NIC facing the external internet. ICS allows clients to use standard Internet tools to access e-mail or the Web, or perform any other operations supported by the Internet. ICS is implemented by setting the TCP/IP connection property. During ICS installation, the ICS DHCP allocator is automatically enabled. Windows 2000 Server uses the ICS DHCP allocator (a simplified DHCP process) to automatically assign clients private IP addresses in the range of 192.168.0.2 to 192.168.254.254 and a class C subnet mask of 255.255.255.0. The server’s NIC which connects to the internal LAN is assigned the “LINKLOCAL Network” static private IP address of 192.168.0.1. This is the IP gateway address for other clients on the LAN. The external NIC can include a standard telephone modem. If so, check the “Enable On-Demand Dialing” option.