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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
106 Switch Management and Operating Concepts
entire name translation, or simply return the address of the
next DNS server if the server receiving the query cannot resolve
the name.
When a DNS server receives a query, it checks to see if the
name is in its subdomain. If it is, the server translates the
name and appends the answer to the query, and sends it back
to the client. If the DNS server cannot translate the name, it
determines what type of name resolution the client requested.
A complete translation is called recursive resolution and
requires the server to contact other DNS servers until the name
is resolved. Iterative resolution specifies that if the DNS server
cannot supply an answer, it returns the address of the next
DNS server the client should contact.
Each client must be able to contact at least one DNS server,
and each DNS server must be able to contact at least one root
server.
The address of the machine that supplies domain name service
is often supplied by a DCHP or BOOTP server, or can be
entered manually and configured into the operating system at
startup.
DHCP Servers
The Dynamic Host Configuration Protocol (DHCP) is used to
dynamically assign a TCP/IP network configuration to network
devices and computers on the network. It also ensures that IP
address conflicts do not occur.
IP addresses are assigned from a pool of free addresses. Each
IP address assigned has a ‘lease’ and a ‘lease expiration period’.
The lease must be periodically renewed. If the lease is expires,
the IP address is returned to the pool of available IP addresses.