70-291: MCSE Guide to Managing a Microsoft Windows Server 2003 Network Chapter 6: Name Resolution

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 2 Objectives Describe the different name types available on Windows Server 2003 View and configure NetBIOS names Describe the host name resolution process Discuss the different methods used to resolve NetBIOS names Configure NetBIOS name resolution using the LMHOSTS file and WINS Troubleshoot name resolution

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 3 Name Types WinSock and NetBIOS are the two standard methods used to access network resources Host name is a name accessed through WinSock DNS domain names consist of an organization name followed by a top-level domain To merge with the worldwide DNS lookup system, you must register your domain name with a registrar Use the hostname command in Windows Server 2003 to view your host name

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 4 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 5 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 6 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 7 Name Types (continued) A NetBIOS name is used to access a resource through NetBIOS All of the networking functions in pre-Windows 2000 operating systems use NetBIOS names NetBIOS names are limited to 15 characters in length and have a 16th character that identifies the target resource or service Use the nbtstat –n command to view the NetBIOS names attached to services

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 8 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 9 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 10 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 11 Name Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 12 Host Name Resolution WinSock applications use more than one method to resolve host names to IP addresses Resolution steps:  Checks to see if the host name being resolved is the same as its own host name  HOSTS file is loaded into cache  DNS cache evaluated  Machine requests information from DNS server  Tries NetBIOS name resolution as a last resort

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 13 Configuring a HOSTS File for Name Resolution HOSTS file is a simple text file Contents of a HOSTS file is a list of IP addresses and host names IP address on the left, one or multiple spaces, host name on the right # denotes a comment

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 14 Configuring a HOSTS File for Name Resolution (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 15 Managing the DNS Cache The DNS cache is queried before DNS is contacted The DNS cache contains the contents of the HOSTS file as well as previous DNS query results DNS query results are not stored in cache permanently To view the contents of the DNS cache, simply run the command ipconfig /displaydns To purge the cache, simply run the command ipconfig /flushdns

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 16 Managing the DNS Cache (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 17 Using DNS for Name Resolution Your computer will use whatever DNS server is specified in the TCP/IP settings for name resolution DNS may use either a forward or reverse lookup scheme

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 18 Using DNS for Name Resolution (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 19 Forward Lookup The most common task for a DNS server is to resolve a host name to an IP address Resolving host names within an organization is a two-packet process 13 root servers control the overall DNS lookup process for the entire Internet A recursive lookup is used whenever the local DNS server does not hold the requested information

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 20 Forward Lookup (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 21 Reverse Lookup Involves the conversion from an IP address to host name Often performed for the system logs of Internet services Reverse lookup DNS information is maintained by the organization that has been assigned an entire class of addresses

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 22 DNS Record Types DNS records are created on a DNS server to resolve queries Each type of record holds different information about a service, host name, IP address, or domain DNS has the ability to hold many different record types

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 23 DNS Record Types (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 24 Using NSLOOKUP The utility NSLOOKUP queries DNS records NSLOOKUP can be used from a command prompt to resolve host names NSLOOKUP is most powerful in interactive mode You can use NSLOOKUP to view any DNS records available for a zone

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 25 NetBIOS Name Resolution There is more than one name resolution method Methods include: NetBIOS name cache WINS Broadcast LMHOSTS files Broadcasts can slow down network communication The NetBIOS name cache and WINS are both used to resolve computer names before the client attempts a broadcast

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 26 NetBIOS Name Resolution (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 27 Using a LMHOSTS File for Name Resolution LMHOSTS file is a simple text file The LMHOSTS file stores NetBIOS names and their associated IP addresses Each entry in the file has the IP address on the left, one or multiple spaces, then the NetBIOS name on the right Lines that begin with a # symbol are comments

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 28 Using a LMHOSTS File for Name Resolution (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 29 Using WINS for Name Resolution Each NetBIOS name is tied to a service A WINS server is a central repository for NetBIOS name and service information When WINS is implemented, all client computers and servers must be configured to use the WINS server

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 30 Using WINS for Name Resolution (continued) WINS offers several benefits over other NetBIOS name resolution methods Four common tasks of WINS include: Name registration Name renewal Name release Name query

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 31 Using WINS for Name Resolution (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 32 Name Registration When a WINS client boots up, it performs a name registration Name registration places NetBIOS information about the client into the WINS database It is a two-packet process The first packet is a name registration request The second packet is a name registration response

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 33 Name Registration (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 34 Name Renewal Each NetBIOS name registration is assigned a TTL When the TTL is half completed, the WINS client attempts to refresh the registration Name renewal is a two-packet process The first packet is a name refresh request The second packet is a name refresh response

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 35 Name Renewal (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 36 Name Release When a computer is properly shut down, it contacts the WINS server and releases its NetBIOS name The first packet in the release process is a name release request The second packet in the process is a name release response

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 37 Name Release (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 38 Name Query A name query is used to resolve a NetBIOS name to an IP address The first packet in the name query process is a name query request The second packet is a name query response The response is either the IP address or a message indicating that the address could not be resolved

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 39 Name Query (continued)

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 40 Troubleshooting Name Resolution Failure of name resolution will prevent users from connecting to resources on the network Determine whether there are any TCP/IP connectivity problems Check the HOSTS file and DNS settings if host name resolution is failing If NetBIOS resolution fails, check the NetBIOS name, TCP/IP settings, and LMHOSTS file

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 41 Summary Host names are used by WinSock applications to access network resources NetBIOS names are used by NetBIOS applications The Internet uses FQDNs to refer to resources The computer name supplied during a Windows Server 2003 installation determines the host name and NetBIOS name for the computer Host name resolution is performed in four steps Forward lookup resolves host names to IP addresses Reverse lookup resolves an IP address to a host name

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 42 Summary (continued) A recursive lookup is performed when a local DNS server queries the root servers on the Internet on behalf of a DNS client Common DNS record types include: A, MX, CNAME, NS, SOA, SRV, AAAA, and PTR The NSLOOKUP utility can verify that a DNS server is configured with the proper records The resolution of NetBIOS names to IP addresses is critical for pre-Windows 2000 clients

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 43 Summary (continued) There are four ways a NetBIOS name can be resolved: NetBIOS name cache, WINS, broadcast, and LMHOSTS file NetBIOS node types may be used to alter the type and order of NetBIOS name resolution Broadcast name resolution is not suitable for large networks because it doesn’t work across routers An LMHOSTS file is not suitable for large networks because the file needs to be copied to every server and workstation

70-291: MCSE Guide to Managing a Microsoft Windows Server Network 44 Summary (continued) A WINS server is a central repository for resolving NetBIOS names and offers several benefits over other NetBIOS name resolution methods Four common tasks are performed by a WINS server: name registration, name renewal, name releasing, and name querying When a name is registered with a WINS server, the client is assigned a TTL If the name is not renewed by the end of the TTL, the client stops using the name