Foundation Summary

The "Foundation Summary" is a condensed collection of material for a convenient review of this chapter's key concepts. If you are already comfortable with the topics in this chapter and decided to skip most of the "Foundation Topics" material, the "Foundation Summary" will help you recall a few details. If you just read the "Foundation Topics" section, this review should help further solidify some key facts. If you are doing your final preparation before the exam, the "Foundation Summary" offers a convenient and quick final review.

Table 3-5 DNS Concepts



Well-known port numbers

UDP Port 53, TCP Port 53

ip host name [tcp-port-number] ip address1 [ip address2...ip address8]

Configured locally to assign a host name with up to 8 IP addresses

no ip domain-lookup

Disables the IP DNS-based host name-to-address translation

ip domain-name name

Defines a default domain name that the Cisco IOS Software uses to complete unqualified host names

ip domain-list name

Defines a list of default domain names to complete unqualified host names

ip name-server ip address

Specifies the address of one or more name servers to use for name and address resolution; up to six name servers permitted

Table 3-6 TFTP Concepts



Well-known port numbers

UDP Port 69 (UDP is typically the only supported protocol for TFTP produced by vendors) and TCP Port 69

copy tftp flash

Cisco IOS command to copy images from a TFTP server


Only filename and directory name are methods used to secure transfers

Table 3-7 Secure Shell (SSH) Concepts



Well-known port number

TCP port 443.


HTTP traffic runs over a secure connection.

Service/client authentication

SSH uses a client server model where clients request secure connections to a host device, such as with a credit card transaction over the World Wide Web.

Table 3-8 SNMP Concepts



Well-known port numbers

UDP 161 (SNMP servers) and UDP 162 (SNMP clients).

SNMP managed devices

An SNMP managed device is a network node that contains an SNMP agent and resides on a managed network. Managed devices collect and store management information and make this information available to Network Management System using SNMP.

SNMP agent

SNMP Agent is a network management software module that resides in a managed device. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.

Table 3-9 SMTP Concepts



Well-known port numbers

TCP 25 and UDP 25

HELO command

Used in communications between host and client

Table 3-10 NTP Concepts



Well-known port numbers

TCP 123 and UDP 123.

ntp master 1-15

Defines stratum value between 1 and 15.

clock set hh:mm:ss day month year

Manually sets clock on a Cisco router.

ntp peer ip-address [version number] [key keyid] [source interface] [prefer]

Defines NTP peers.

ntp authenticate

Enables authentication.

ntp authentication-key number md5 value

Defines NTP authentication key and password.

ntp trusted-key key-number

Defines NTP to authenticate NTP session; key-number is the authentication key to be trusted.

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