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Chapter 7

Managing a Cisco Internetwork

It doesn't know my name, or what command I am trying to type, so it tries

to resolve this through DNS. This is annoying for two reasons: first, because
it doesn't know my name, and second, because I need to wait for the name
lookup to time out. You can prevent the default DNS lookup by using the no
ip

domain-lookup command on your router from global configuration mode.

If you have a DNS server on your network, you need to add a few com-

mands to make DNS name resolution work:

The first command is ip domain-lookup, which is turned on by
default. It only needs to be entered if you previously turned it off (with
the no ip domain-lookup command).

The second command is ip name-server. This sets the IP address
of the DNS server. You can enter the IP addresses of up to six servers.

The last command is ip domain-name. Although this command is
optional, it should be set. It appends the domain name to the host-
name you type in. Since DNS uses a fully qualified domain name
(FQDN) system, you must have a full DNS name, in the form
domain.com

Here is an example of using these three commands:

Todd2509#config t

Enter configuration commands, one per line. End with

CNTL/Z.

Todd2509(config)#ip domain-lookup

Todd2509(config)#ip name-server ?

A.B.C.D Domain server IP address (maximum of 6)

Todd2509(config)#ip name-server 192.168.0.70

Todd2509(config)#ip domain-name lammle.com

Todd2509(config)#^Z

Todd2509#

After the DNS configurations are set, you can test the DNS server by using

a hostname to ping or telnet a device, as shown below.

Todd2509#ping 2501b

Translating "2501b"...domain server (192.168.0.70) [OK]

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.10.2, timeout is

2 seconds:

!!!!!

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