Chapter 6: Introduction to the Internet Protocol

What allows a server to distinguish among different simultaneous requests from the same host?

Port numbers.

What two transport layer protocols does a DNS server use?

TCP port 53 for zone transfers and UDP port 53 for name resolution.

What layer 4 protocol is used for a telnet connection, and what is the default port number?

23.

What well-known port numbers do SMTP, POP3, RDP, and IMAP4 servers use?

25, 110, 3389, 143.

You need to have secure communications using HTTPS. What port number is used by default?

443.

Which destination transport layer protocol and port number does a TFTP client use to transfer files over the network?

69.

Describe the DHCP Discover message.

A client that sends out a DHCP Discover message in order to receive an IP address sounds out a broadcast at both layer 2 and 3. Layer 2 is all Fs in hex, or FF:FF:FF:FF:FF:FF. Layer 3 is 255.255.255.255, which means all networks and all hosts. It uses UDP at the transport layer, also called host-to-host layer.

What might be the problem if a DHCP client suddenly finds itself in a different IP subnet from the one it should be in?

A rogue DHCP server has been introduced to the network and is handing this device an incorrect lease.

What protocol is used to find the hardware address of a local device?

ARP.

The OSI model has severl layers and the DoD has four. At which layer does SMTP work in both models?

Application.

Which services use UDP?

DHCP, SNMP, TFTP.

You want to implement a mechanism that automates the IP configuration, including IP address, subnet mask, default gateway, and DNS information. Which protocol will you use to accomplish this?

DHCP.

What uses both TCP and UDP?

DNS.

If you can ping by IP address but not by hostname, or FQDN, which of the following port numbers is related to the server process that is involved?

DNS; port 53.

Name the protocol that uses both TCP ports 20 and 21.

FTP.

What layer in the IP stack is equivalent to the transport layer of the OSI model?

Host-to-Host.

Which protocol dynamically reports errors to source hosts by using IP directly to build packets?

ICMP uses IP directly to build error-reporting packets that are transmitted back to the originating source host when isseus arise during the delivery of data packets. ICMP is also used during ping and some traceroute operations.

What protocol is at the heart of the ping and tracert commands in a Windows operating system?

ICMP.

What might cause your email to stop functioning properly when you change internet service providers?

Most ISPs have their own mail servers. When you switch service, you might need to point your mail application to the servers provided by the new ISP.

You ened to make sure that the time is consistent across all your network devices. What protocol do you need to run?

Network Time Protocol.

You need to have a connection to run applications that are installed on only your desktop computer at your office. Which protocol will provide a GUI interface to your work computer?

RDP.

You need to transfer files between two hosts. Which two protocols can you use?

SCP (Secure Copy Protocol), FTP.

Which services uses TCP?

SMTP, FTP, HTTP.

Which protocols are used by the email servers to exchange messages with one another?

SMTP.

Which protocols can use TCP and UDP, permits authentication and secure polling of network devices, and allows for automated alerts and reports on network devices?

SNMP.

You need to log in to a Unix server across a network that is not secure. Which of the following protocols will allow you to remotely administrator this server securely?

SSH.

Which TCP/IP protocols are used at the application layer?

Telnet, FTP, TFTP.

What would cause a server that you can ping not to provide the particular TCP/IP service, such as FTP, HTTP, and so on, that you expect it to offer?

The service might not be running currently on the server. Or, the firewall between the client and server has blocked the protocol in question from passing.

Which statements are true regarding ICMP packets?

They can provide hosts with information about network problems and are encapsulated with IP datagrams.

Which Unix command is used for terminal emulation in the same way Telnet is used?

rlogin