Section 4. Understanding TCP/IP Flashcards
Q01-What is the Internet Protocol (IP)?
IP is a connectionless protocol that provides best-effort delivery and routing of packets. IP has the following characteristics: Operates at Layer 3 (network) of the Open Systems Interconnection (OSI) reference model and the Internet layer of the TCP/IP (Internet) model. Is connectionless, providing best-effort delivery of packets. Uses hierarchical addressing. Has no built-in data recovery. Each packet is treated independently; thus each packet can travel a different way to its destination. Operates independently of the medium that is carrying the data.
Q02-What is an IP address used for?
An IP address uniquely identifies a device on an IP network.
Q03-How many bits are in an IPv4 address? In an IPv6 address?
IPv4: 32 bits IPv6: 128 bits
Q04-An IP address is a hierarchical address that consists of what two parts?
An IP address is a hierarchical address that consists of the following two parts: Network ID: Describes the network to which the IP address or device belongs Host ID: The ID that identifies a specific host IP addresses include the use of a subnet mask that is responsible for deciphering which part of the IP address is the network and which part is the host.
Q05-What are the different classes of IP addressing and the address ranges of each class?
The different classes of IP addressing and their ranges are as follows: Class A: 1.0.0.0 to 126.255.255.255 Class B: 128.0.0.0 to 191.255.255.255 Class C: 192.0.0.0 to 223.255.255.255 Class D: 224.0.0.0 to 239.255.255.255 (Multicasting) Class E: 240.0.0.0 to 255.255.255.254 (Reserved) 127.0.0.0 is also a Class A network, but it is reserved for the loopback, or “localhost,” IP—the IP address of the TCP/IP software itself.
Q06-What are the five types of reserved IPv4 addresses?
The five reserved IPv4 addresses are Network address: The address of the network is an IP address that has binary 0s in all the host bit positions. Direct broadcast address: An address for each network that allows communication to all hosts on a network. The direct broadcast address has all 1s in the host bit positions. Local broadcast address: Used to allow hosts to communicate with all hosts on a local network. The address used is 255.255.255.255. Local loopback address: Used to let the system send a message to itself for testing. This address is 127.0.0.1. All zeros address: Used to indicate hosts in “this” network and used only as a source address.
Q07-What does RFC 1918 define?
RFC 1918 defines reserved (private) networks and addresses that are not routed on the Internet. These addresses are as follows: 10.0.0.0 to 10.255.255.255 172.16.0.0 to 172.31.255.255 192.168.0.0 to 192.168.255.255 They are used as internal private addresses within a corporation or home network. Private addresses are widely used today, and they employ mechanisms such as Network Address Translation (NAT) and Port Address Translation (PAT) to assist with “stretching” the current IPv4 address space. This stretching is done by translating private IP addresses to public routable IP addresses on the Internet, thus ensuring that private hosts can communicate externally without having a public IP address directly configured.
Q08-If an IP addressed device wants to communicate with all devices on the local network, what is the destination IP address of its broadcast?
The destination IP address is 255.255.255.255. This address is also called the local broadcast address.
Q09-What is special about IP address 127.0.0.1?
127.0.0.1 is the loopback address. The loopback address is used to test the proper installation of the IP stack.
Q10-In a default Class A network, how many octets are used for host addresses?
Three octets are used for host addresses. One octet consists of 8 bits; thus a default Class A network uses 24 bits for host addresses. The maximum number of hosts a Class A network can have is 16,777,214 (224 – 2).
Q11-How many hosts are available for use in a default Class B network?
65,534 addresses are available. A default Class B network uses 16 bits for host addresses; thus 216 – 2 = 65,534.
Q12-How many hosts are available for use in a default Class C network?
254 hosts are available. A default Class C network uses 8 bits for host addresses. Thus 28 – 2 = 254.
Q13-What is DNS?
The Domain Name System (DNS) converts domain names or host names into IP addresses. Instead of having to remember a host’s IP address, DNS allows you to use a friendly name to access the host. For example, it is easier to remember http://www.cisco.com than 198.133.219.25.
Q14-On a Windows computer, what command can you use at the command prompt to view the IP information assigned to the PC?
You can use the ipconfig command.
Q15-On a Windows computer, what commands do you use to release an IP address obtained from DHCP and request a new address?
To release the IP address: ipconfig /release To request a new address: ipconfig /renew
Q16-Convert the binary number 01100100 to decimal.
Converting a binary number to decimal is just the reverse of converting a decimal number to binary. When converting from binary, look at the numbers that are considered ON and then find their place value. In the binary number 01100100, the place values 64, 32, and 4 are ON. If you add these place values together, you get the decimal number of 100.
Q17-Convert the binary number 0101011011000010 to hexadecimal.
Converting binary to hex is easier than it looks. No matter how large the binary number, always apply the following conversion: Break the binary number into groups of four, starting from the right and moving left. If the binary number is not divisible by four, add 0s to the left end or until you have four digits in every group. Using this equation, 0101011011000010 is broken into the following groups: 0101 0110 1100 0010. After you have created the groups, you can convert the digits to hex. 0101 is 5 in hex, 0110 is 6, 1100 is C, and 0010 is 2, so this binary number looks like the following in hex: 0x56C2.
Q18-What is the range of binary values for the first octet in Class B addresses?
The first octet for a Class B IP address is 128–191 in decimal, which is 10000000–10111111 in binary. If you see similar questions on the ICND 1 exam, remember the following: Class A addresses always have the high-order bit as 0. For example, 0xxxxxxx. Class B addresses always have the high-order bit as 1 and the second bit as 0. For example, 10xxxxxx. Class C addresses always have the high-order bit and second bit as 1. The third bit is 0. For example,110xxxxx.
Q19-What is the role of the subnet mask in an IP network?
The subnet mask identifies the network and host portion of an IP address. It is used by hosts to identify the destination IP address as either local or remote and is also used by routers to determine the path to route packets.
Q20-How many usable IP addresses are provided in a default Class C network address?
254 usable IP addresses are provided. The default subnet mask for a Class C address is 255.255.255.0, or /24. This means that 24 bits are used for the network number and 8 bits are reserved for hosts. 28 = 256. However, because two addresses are reserved for the network address and broadcast address, the amount of usable IP addresses is 254. The formula to calculate usable IP addresses is 2n–2, where n is the number of host bits.
Q21-Convert the decimal number 167 to binary.
Binary uses only two symbols (1 or 0) instead of ten symbols like decimal. In binary, 1 signifies ON and 0 signifies OFF. To convert a decimal number to binary, each digit represents the number 2 raised to a power exponent based on its position. The following table converts decimal to binary:
To convert a decimal number to binary, first find the largest power of 2 that can fit into the decimal number. If you have the decimal number 167, 128 is the largest power of 2 that fits into this binary number, so 128 is considered ON. Subtracting 128 from 167 leaves you with 39. The next largest power that can fit into 39 is 32, so 32 is considered ON. Subtracting 32 from 39 leaves you with 7, so 4, 2, and 1 are considered ON. This leaves you with the following binary number: 10100111.
Q22-What is the correct network address for host 192.168.10.72/26?
The correct network address is 192.168.10.64.
A 26-bit subnet mask is 255.255.255.192. A quick way to find the network of a given subnet mask is to subtract the last portion of the subnet mask from 256. In this case, 256 – 192 = 64. Assuming that the ip subnet zero command is enabled on the router, the usable networks for a 26-bit subnet mask are as follows:
- 168.10.0
- 168.10.64
- 168.10.128
- 168.10.192
Host 192.168.10.72 falls in the 192.168.10.64 network.