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Cisco- Windows Networking Design Implementation Guide Page 1 of 29 Windows Networking Design Help us help you. ÿþýüûý ùüøý ø÷öû Implementation Guide ýø ÿ Excellent ÿ Good Contents ÿ Average ÿ Fair Introduction ÿ Poor What Is Windows Networking? Domains versus Workgroups ÷öû ýø What Protocol Does It Use? ùýýøý ü üûý Dynamic IP Addressing What Is DHCP? ÿ Yes DHCP Scopes ÿ No DHCP Relay DHCP Options ýûøöû ù öùýýø Cisco DHCP Servers Name Resolution NetBIOS Name Cache Broadcasts LMHOSTS Windows Internet Name Service (256 character limit) Internet DNS øöüþ øüø Name Lookup Order öùüøö The Microsoft LAN Services Browser Name: NetBIOS Names The Startup Process Email: Finding a Computer Viewing the Network Neighborhood Subnet Browsing ÿþýü Broadcast Browsing across Subnets Browsing Any Domain with WINS Turning Off Broadcasts Scaling to Larger Networks Trusted Domains Single Domain Global Trust Master Domain Multiple Master Domains Replicating WINS Modem Access Dial-on-Demand Routing ISDN Access Adtran http://www.cisco.com/warp/public/473/winnt_dg.htm 3/23/2001 Cisco- Windows Networking Design Implementation Guide Page 2 of 29 Motorola BitSURFR Client Software CiscoRemote Lite Examples Example 1 Configuration of Cisco 4700 Router Configuration of Cisco 2511 Access Server Example 2 LMHOSTS Configuration on Claude (a Client in the Marketing Domain) LMHOSTS Configuration on mkt_PDC (Primary Domain Controller for the Marketing Domain) Configuration of Cisco 7500 Router Configuration of an AS5200 in a Stack Group Configuration of Cisco 700 Router Example 3 Configuration of a Cisco 1600 Example 4 Appendix A: Turning Off Broadcast Name Resolution When Using Windows for Workgroups 3.11 Windows 95/98 Windows NT 3.51 Windows NT Registry Entries Finding Rogue Browse Masters Appendix B: Configuring DNS Resolution of WINS Names The DNS Boot File The DNS File for domain.com Introduction The term "networking" covers a broad range of technologies, which, combined together, allow computers to share information. Networking components can be segmented into end-system applications, network operating systems, and networking equipment. A network operating system is software run on all interconnected systems. Examples include Novell NetWare, Sun's NFS (Network File System), AppleShare, and Microsoft's implementation of a network operating system commonly called Windows Networking. Windows Networking is now extensively deployed with millions of nodes. This design guide explains the basic concepts of Windows Networking and provides insight on how to design networks (LANs and WANs) to best utilize this operating system. The guide also explains protocols, naming, and scaling issues associated with Windows Networking. What Is Windows Networking? Windows Networking refers to the networking system shared by the software that comes with all the following Microsoft operating systems or servers: http://www.cisco.com/warp/public/473/winnt_dg.htm 3/23/2001 Cisco- Windows Networking Design Implementation Guide Page 3 of 29 ÿ Microsoft LAN Manager ÿ MS-DOS with LAN Manager client ÿ Windows for Workgroups ÿ Windows 95, 98, and ME ÿ Windows NT and 2000 Microsoft LAN Manager, the LAN Manager client for MS-DOS, and Windows NT 3.1 are not discussed in this document except in an historical context. Domains versus Workgroups Windows Networking has three concepts of a group of related computers- workgroups, domains and a domain hierarchy. Workgroups can be any logical collection of computers; any computer on the network can join an existing workgroup or create a new one. More formal entities, domains are created and managed by a primary domain controller (PDC) process that runs on a Windows NT or Windows 2000 server. A domain has security and administrative properties that a workgroup does not. Each domain must have at least one NT or 2000 server, which is responsible for the PDC process, user account information in the domain, and security within the domain. Windows Networking domains are not the same as Internet domain names as used by the Domain Name System (DNS). A domain hierarchy or Active Directory Hierarchy is a collection of domains organized into parent-child relationships. This convention, introduced with Windows 2000, enables easier searching through multiple domains in a single query (among other things). This hierarchy maps closely to a DNS namespace. What Protocol Does It Use? Prior to Windows 2000, Windows Networking used the NetBIOS protocol for file sharing, printer sharing, messaging, authentication, and name resolution. A pure Windows 2000 installation would require NetBIOS only for interoperability with earlier versions of Windows Networking using the flat NetBIOS namespace. NetBIOS is a session-layer protocol that can run on any of the following transport protocols: ÿ NetBEUI (NetBIOS over LLC2) ÿ NWLink (NetBIOS over Internetwork Packet Exchange [IPX]) ÿ NetBIOS over TCP (NBT) Although Microsoft recommends that clients use only one transport protocol at a time for maximum performance, this setup is only the default for Windows 2000. You should pick a protocol to use for your entire network, preferably TCP/IP, and then turn the other protocols off because the NetBIOS name service maintains information about computer names (a name space) separately for each transport. Name spaces do not interact with each other; each transport operates as a separate network. http://www.cisco.com/warp/public/473/winnt_dg.htm 3/23/2001 Cisco- Windows Networking Design Implementation Guide Page 4 of 29 NetBEUI (NetBIOS over LLC2) is the least scalable of the three protocols because it must be bridged. NetBEUI is included only to support very old services (for example, old versions of LAN Manager). NetBEUI does not require any client address configuration. There is no fixed limit to the number of Windows clients can have with NetBEUI, but it is common for this solution to run into performance problems as the number of clients in a single bridge group goes above 50 to 100 users. The flat topology and reliance on broadcasts does not scale, especially when traffic must traverse a WAN link. NWLink is recommended only for networks already running IPX that cannot be upgraded to use TCP/IP. Similar to NetBEUI, NWLink requires no client address configuration. NWLink uses IPX type-20 packets to exchange registration and browsing information. To forward type-20 IPX packets across Cisco routers, you must configure ipx type-20 propagation on each interface on every router on your network. It is recommended to utilize NetBIOS over TCP (NBT) for most networks, or anytime the network includes a WAN. Since NBT uses TCP/IP, each computer must be configured to use a static IP address, or to fetch an IP address dynamically with the Dynamic Host Configuration Protocol (DHCP). For ease of network administration, it is highly recommended to use DHCP; for optimum network performance, it is highly recommended to use a (Windows Internet Name Service) WINS server as well. A WINS server allows clients to get browsing information without having to broadcast requests everytime. There is a direct correlation between the number of broadcasts in a network and network performance; broadcasts are necessary for a network to function, but minimizing them can be critical. Cisco recommends that most customers use TCP/IP for Windows Networking. The bulk of this design guide focuses on designs using NBT. Dynamic IP Addressing What Is DHCP? Manually addressing TCP/IP clients is both time consuming and error prone. To solve this problem, the Internet Engineering Task Force (IETF) developed DHCP, the Dynamic Host Configuration Protocol. DHCP is designed to automatically provide clients with a valid IP address and related configuration information (see the section DHCP Options below). Each range of addresses that a DHCP server manages is called a scope. DHCP Scopes You must configure a range of addresses for every IP subnet where clients will request a DHCP address; each range of addresses is called a DHCP scope. You can configure a DHCP server to serve several scopes since the DHCP server or servers do not need to be physically connected to the same network as the client. If the DHCP server is on a different IP subnet from the client, then you need to use DHCP relay to forward DHCP requests to your DHCP server. DHCP Relay http://www.cisco.com/warp/public/473/winnt_dg.htm 3/23/2001 Cisco- Windows Networking Design Implementation Guide Page 5 of 29 DHCP relay typically runs on a router and the relay support is available on Windows NT Server version 4.0 and Windows 2000 Server. On Cisco 700 series routers, you can turn on DHCP relay with the set dhcp relay command. You can turn on DHCP relay on a Cisco IOS router by configuring ip helper-address with the address of the DHCP server on each interface that will have DHCP clients. The ip helper-address command forwards many other IP broadcasts, including DNS, Trivial File Transfer Protocol (TFTP), and NetBIOS name service packets. To forward only DHCP requests, see the following example configuration. For more information, see the "Configuring Broadcast Handling" section in the Network Protocols Configuration Guide, Part I. no ip forward-protocol udp tftp no ip forward-protocol udp dns no ip forward-protocol udp time no ip forward-protocol udp netbios-ns no ip forward-protocol udp netbios-dgm no ip forward-protocol udp tacacs ip forward-protocol udp bootpc ! interface ethernet 0 ip helper-address 172.16.12.15 interface ethernet 1 ip helper-address 172.16.12.15 DHCP Options In addition to its IP address, a DHCP client can get other TCP/IP configuration information from a DHCP server, including the subnet mask, default gateway, and DNS information. These pieces of information, called DHCP options, can be configured in the DHCP Manager on your Windows NT or Windows 2000 DHCP server. Figure 1: Microsoft's DHCP Manager http://www.cisco.com/warp/public/473/winnt_dg.htm 3/23/2001 Cisco- Windows Networking Design Implementation Guide Page 6 of 29 If your clients are using Windows Internet Name Service (WINS) for name resolution (discussed later), you should configure the address of the WINS server and the WINS node type.