IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
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- Resolver
The resolver is the program which sends the DNS queries to one of the
defined name servers. A name server which is unable to perform name
resolution can also act as resolver, sending the query to a name server
outside the domain. Similarly the resolver interprets the responses received
from the name server and sends information back to the programs which
have requested it.
DNS server configuration - initial steps
With a NetWare 4.11 server, DNS is configured via UNICON.NLM. First of
all DNS Client Access needs to be activated. This is done via Configure Server
Profile - Manage Global Objects. At least one name server which performs
address resolution must be listed. A maximum of three name servers can be
entered. To speed up entry of a large address area and ensure that name
resolution can be performed, the entries for the three name servers should be
utilised. The sequence in which the name servers are listed determines the
query sequence and should be determined in the manner which results in the
fastest name resolution.
The first name server can be the main DNS server of the authority or
company. Even if this server cannot resolve every host outside its own
domain, it allows host names to be resolved rapidly within the organisation.
The second name server can belong to the Internet Service Provider (ISP),
enabling access to a wider data pool of host names. This has the effect that due
to the higher utilisation, the remoteness and the available bandwidth,
resolution is usually somewhat slower than with the local name server. If
redundancy of the local domain is a priority, then the server with the writeprotected
copy of the DNS database (secondary name server) should be
registered as the second name server.
The third name server defined can be a so-called root server. This type of
server holds the data for all the registered domains. A list of root servers can
be obtained from ftp://rs.internic.net/netinfo/root-servers.txt.
Configuration of the DNS server
The configuration and administration functions for the Domain Name System
are accessed by selecting Manage Services - DNS from the UNICON.NLM
main menu. To set up a master database or a write-protected replica database,
the Administer DNS menu option should be selected.
The domains and zones for which the primary name server is authorised are
entered by selecting Manage Services - DNS - Administer DNS - Manage
Master Database - Delegate Subzone Authority from the UNICON.NLM main
menu.
The DNS database entries are entered via Manage Services - DNS -
Administer DNS - Manage Master Database. With a standard implementation
of DNS, the Start of Authority (SOA), which identifies the starting point for
the authority of a zone within the DNS hierarchy, and the record type Name
Server (NS) must be entered. The primary name server must receive entries
for all the secondary name servers of the zone. Linking of this zone with the
DNS hierarchy is achieved through name server entries for primary name
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IT-Baseline Protection Manual: Oktober 2000
Querying of the DNS
server and interpretation
of the responses
Register three name
servers
Enter all the secondary
name servers in the
database