D-Link DES-3326SR, User Manual

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DES-3326SR Layer 3 Fast Ethernet Switch User’s Guide
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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.
Usually, it is a network policy to assign the same IP address to
a given network device or computer each time.
If the IP address lease expires, the network device sends a
message to the DHCP server requesting a lease renewal. The
DHCP server can send an acknowledgement containing a new
lease and updated configuration information.
If an IP address lease cannot be renewed, the network device or
computer sends a request to all local DHCP servers attempting
to renew the lease. If the DHCP returns a negative