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IP Configuration 289
Three names are statically configured in this case--Mays, Aaron, and Mantle. When logged
into Cooperstown, any command referring to Mays, Aaron, or Mantle will resolve into the IP
addresses shown in the ip host command.
DNS configuration is shown toward the end of the configuration. For names that do not include
the full domain name, the ip domain-name command defines the domain name that should be
assumed by the router. The IP addresses of the name servers are shown in the ip name-server
command. Up to six DNSs can be listed; they are searched for each request sequentially based
on the order in the command. Finally, the ip domain-lookup command enables the IOS to ask
a name-server. IP domain-lookup is the default; no ip domain-lookup disables the DNS client
function.
The name Cooperstown in the hostname command is shown to make a point that it is not a
definition that creates a correlation between a name and an IP address. The hostname command
tells this device what its own name is; any command referring to a host name and with
Cooperstown typed as the host name would need either an ip host command or a DNS
resolution for Cooperstown for the command to work.
The show ip host command lists the static entries, in addition to any entries learned from a DNS
request. Only the three static entries were in the table, in this case. The term perm in the output
implies that the entry is static.
Telnet on the IOS
The telnet IOS EXEC command can be particularly useful when working with more than one
router or switch at the same time. If you prefer, you could open more windows on your desktop
and Telnet to the various routers and switches. However, if you log in to one router and then
want to Telnet to others, this subsection provides you with some interesting capabilities of the
IOS Telnet client and server.
Each IOS runs a Telnet server automatically. Just like other Telnet servers, it listens on port 23.
The telnet EXEC command is a Telnet client, which can be used to Telnet to many other
devices, not just another router or switch. So, many of the same assumptions you make about
Telnet are true for the IOS-based Telnet client and server.
The convenient use of the suspend function of the Telnet client is one of the best features of the
Telnet client. For this discussion, you will need to refer to the network diagram in Figure 5-30.
ch05.fm Page 289 Monday, March 20, 2000 5:06 PM