| 
252DX-600/800APR 2002Edition 1.07.5.8. NS (Name Server) RecordThe Name Server record specifies the other name servers for a domain. The syntax for a name serverrecord is shown below: IN NS An example of a name server record follows below:@ IN NS nwmgr.mgcs.mei.co.jpThe "@" symbol indicates the local domain. The server "nwmgr" in the domain "mgcs.mei.co.jp" is thename server.7.5.9. MX (Mail Exchange) RecordThe Mail Exchange (MX) record specifies the name of the host that processes mail for this domain. If youlist multiple mail servers, you can set a preference number (value) that specifies the order in which the mailserver should be used. Note that lower values indicate higher precedence, and that mailers are supposedto randomize same-value MX hosts so as to distribute the load evenly if values are equal. If the firstpreferred mail server does not respond, the second one is contacted, and so on.If you want a host to receive its own mail, you should create an MX record for your host’s name, pointing atyour host’s name. The syntax of this record is shown below: IN MX For a more detail, please refer to RFC974 document at URL http://www.ietf.org/.7.5.10. Reverse LookupThis is a special domain for allowing address to name mapping. As Internet host addresses do not fallwithin domain boundaries, this special domain was formed to allow inverse mapping. The IN-ADDR.ARPAdomain has four labels preceding it. These labels correspond to the 4 octets of an Internet address. All fouroctets must be specified even if an octet contains zero. The Internet address 128.32.0.4 is located in thedomain 4.0.32.128.IN-ADDR.ARPA. This reversal of the address is awkward to read but allows for thenatural grouping of hosts in a network.7.5.11. ForwardingA Slave Server is a server that always forwards queries it cannot satisfy from its cache, to a fixed list offorwarding servers instead of interacting with the name servers for the root and other domains. The queriesto the forwarding servers are recursive queries. There may be one or more forwarding servers, and they aretried in turn until the list is exhausted. A Slave and forwarder configuration is typically used when you do notwish all the servers at a given site to interact with the rest of the Internet servers. A typical scenario wouldinvolve a number of workstations and a departmental timesharing machine with Internet access. Theworkstations might be administratively prohibited from having Internet access. To give the workstations theappearance of access to the Internet domain system, the workstations could be Slave servers to thetimesharing machine, which would forward the queries and interact with other name servers to resolve thequery before returning the answer. An added benefit of using the forwarding feature is that the centralmachine develops a much more complete cache of information that all the workstations can take advantageof. The use of Slave mode and forwarding is discussed further under the description of the named bootfilecommands.There is no prohibition against declaring a server to be a slave even though it has primary and/or secondaryzones as well; the effect will still be that anything in the local server’s cache or zones will be answered, andanything else will be forwarded using the forwarders list.For more detail, please refer to published book (i.e. DNS and BIND etc) provided from O’ Reilly &Associates, Inc. |
