TCP/IP and the DoD Model
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An important thing to remember about DNS is that if you can ping a device
with an IP address but cannot use its FQDN, then you might have some type
of DNS configuration failure.
Dynamic Host Configuration Protocol (DHCP)
Dynamic Host Configuration Protocol (DHCP)
gives IP addresses to hosts.
It allows easier administration and works well in small-to-even-very-large
network environments. All types of hardware can be used as a DHCP server,
including a Cisco router.
DHCP differs from BootP in that BootP gives an IP address to a host, but
the host's hardware address must be entered manually in a BootP table. You
can think of DHCP as a dynamic BootP. But remember that BootP is also
used to send an operating system that a host can boot from. DHCP can't
do that.
But there is a lot of information a DHCP server can provide to a host
when the host is requesting an IP address from the DHCP server. Here's a list
of the information a DHCP server can provide:
IP address
Subnet mask
Domain name
Default gateway (routers)
DNS
WINS information
A DHCP server can give us even more information than this, but the items
in that list are the most common.
The Host-to-Host Layer Protocols
The main purpose of the Host-to-Host layer is to shield the upper-layer
applications from the complexities of the network. This layer says to the
upper layer, "Just give me your data stream, with any instructions, and I'll
begin the process of getting your information ready to send."
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