Chapter 3 “Do I Know This Already?” Quiz Answers

1: RFC 1700 defines what well-known ports for DNS?

  1. TCP port 21

  2. TCP port 23

  3. UDP port 21

  4. UDP port 53

  5. TCP/UDP port 53

A1: Answer: e

DNS is permitted by RFC 1700 to use both TCP/UDP port 53. Typically UDP is vendor-configured for UDP port 53.

2: What supplies DNS security?

  1. A default username/password pairing

  2. A TFTP directory

  3. A filename

  4. A domain name

  5. None of the above

A2: Answer: e

DNS has no form of security, so any device can request name-to-IP address mappings.

3: What IOS command will stop a Cisco router from querying a DNS server when an invalid IOS command is entered on the EXEC or PRIV prompt?

  1. no ip domain-lookup

  2. no ip dns-lookup

  3. no ip dns-queries

  4. no exec

A3: Answer: a

To disable DNS query lookup, the IOS command ...

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