You have added a new router to your network using all of the default settings. You can connect to everything by
IP address, but the router doesn’t seem to be resolving names to IP addresses. The DNS server is in a directly
connected network.
Which of the following is most likely the problem?

A.
You configured an incorrect IP address for the DNS server

B.
You configured an incorrect default gateway on the router

C.
You failed to execute the ip domain lookup command

D.
You failed to create an IP helper address

Explanation:
The most likely problem is that you configured an incorrect IP address for the DNS server. Although it is
impossible to know without executing the show run command, the other options can all be eliminated, making
this the most likely option.
Even if the router has an incorrect default gateway, or has no default gateway configured, the router should be
able to connect to resources by name if it can connect to them by IP address. The gateway will only be required
if the DNS server is in a network not found in the routing table of the local router. Since the network containing
the DNS server is directly connected, that network is automatically in the routing table.
The ip domain lookup command is enabled by default, so it does not need to be executed. If the scenario had
not stated that all defaults were in place, it could be verified with the show run command as shown below,
where line 4 indicates the ip domain lookup command is disabled:
routera# show run
<output omitted>
hostname routera
no ip domain lookup
ip domain name acme.com
ip name-server 192.31.1.6
It is not required to have an IP helper address for DNS to function for the router. It is only required by the nonrouting devices connected to the router, and only for those that are not on the same network with their DHCP
server.
Objective:
Infrastructure Services
Sub-Objective:Troubleshoot client- and router-based DHCP connectivity issues