Reach it by address but not by name: fix an A record, then give R1 a name server

Steps

1. Place the devices and cable them as the Topology lists. Use the automatic connection type (the lightning-bolt cable) for every link, so Packet Tracer picks straight-through or cross-over for you. Give PC1, SRV1 and SRV2 their addresses and gateway in Desktop > IP Configuration, and set the DNS Server field on all three to 192.168.20.53. Then configure R1:

Router> enable
Router# configure terminal
Router(config)# hostname R1
R1(config)# interface GigabitEthernet0/0/0
R1(config-if)# ip address 192.168.20.1 255.255.255.0
R1(config-if)# no shutdown
R1(config-if)# end

2. Before any DNS exists, mistype a command on R1 and wait for the prompt to come back:

R1# shwo
Translating "shwo"...domain server (255.255.255.255)
% Unknown command or computer name, or unable to find computer address

IOS treated the unknown word as a host name and looked it up. The address in brackets is the clue the lesson describes: 255.255.255.255 means R1 has no ip name-server, so it broadcast the query and waited for an answer that never came. 3. Build the zone. On SRV1 open Services > DNS and set DNS Service to On. Add an A Record with Name www.example.com and Address 192.168.20.80. Then add a CNAME with Name intranet.example.com and Host Name www.example.com. The CNAME holds no address of its own: a client that asks for intranet.example.com is sent on to www, and the address comes from www's A record. 4. Query both names from PC1's Command Prompt, then open Desktop > Web Browser and browse to http://intranet.example.com: SRV2's default page loads.

C:\> nslookup www.example.com
C:\> nslookup intranet.example.com

Both answers end with the address 192.168.20.80, the first straight from the A record and the second through the alias. 5. Break it the way a server move often goes wrong. On SRV1, select the www.example.com A record, change its Address to 192.168.20.81 and click Save. On PC1, close and reopen the Web Browser, then browse to http://intranet.example.com again: the page no longer loads. Now ask the lesson's question:

C:\> ping 192.168.20.80
C:\> nslookup www.example.com

The ping by address gets replies, and nslookup returns 192.168.20.81, an address nobody holds. The link, the switch and the server are fine; the A record is wrong. Nothing about the CNAME is wrong either: as in the lesson's deleted-target case, the alias is only as good as the A record of the name it points to. 6. Fix the record: set the www.example.com A record's Address back to 192.168.20.80 and click Save. Close and reopen PC1's Web Browser, browse to http://intranet.example.com, and the page loads again. On a busy network the fix would take effect only as cached answers expire, which is what the TTL controls. 7. Give R1 a name server and a domain suffix, then use a name from R1. Packet Tracer accepts the older spelling ip domain-name, which the lesson writes as ip domain name:

R1# configure terminal
R1(config)# ip name-server 192.168.20.53
R1(config)# ip domain-name example.com
R1(config)# end
R1# ping www.example.com

The Translating message now names 192.168.20.53 instead of the broadcast address, and the pings go to 192.168.20.80. Mistype shwo once more: the message names 192.168.20.53 too, and the prompt returns much faster, because a server now answers. Many engineers add no ip domain-lookup on lab routers to stop the pause, but that would also stop ping www.example.com from working, so leave lookup on here.