Ch. 3 Networking Devices

Network Interface card The network interface card (NIC) allows a device to send and receive messages over the transmission media.

Transceiver A transceiver (short for transmitter/receiver) sends signals to and receives signals from the network. It translates the parallel data stream of the computer to the serial data stream of the network and vice versa. Most transceivers are now built into network interface cards (NICs).

It modulates digital data from the PC into analog data and transmits it on a telephone network. It demodulates analog data from a telephone network into digital PC data. Modem is shorthand for modulator/demodulator. Its job is to convert (or modulate) digital data from a PC into analog telephone signals and transmit them through a telephone network.

Media converter Use a media converter to convert from one media type to another media type within the same architecture. Use a bridge to connect two devices that use different network architectures, for example to connect a wired network to wireless clients. A hub or a repeater connect devices using the same media type.

Layer 1 A media converter operates at the OSI model layer 1 (Physical layer). The media converter translates frames into bits and transmits them on the transmission medium. At layer 2, the MAC address is added to make the data into a frame. At layer 3, the IP address is added to the packet. A media converter does not alter or use the MAC address or the IP address.

SFP GBIC Older network adapters used an external transceiver that matched the media type. While nearly all current network adapters come with a built-in transceiver type, new devices, such as switches and routers, use transceiver modules that allow you to modify the media type of a port by changing the transceiver. Transceiver modules include the following: GBIC (gigabit interface converter) is a larger-sized transceiver that fits in a port slot and is used for Gigabit media including copper and fiber optic. SFP (small form-factor pluggable) is similar to a GBIC but with a smaller size. An SFP is sometimes called a mini-GBIC XFP transceiver is similar in size to an SFP but is used for 10 Gigabit networking.

C0-34-FF-15-01-8E A MAC or hardware address is a unique identifier hard coded on every network adapter card. A valid MAC address has a total of 12 hexadecimal numbers. Hexadecimal numbers contain the numbers 0 to 9 and letters A to F. Valid values in a MAC address range anywhere from 00 to FF. Note that one of the answers would be valid MAC address except it uses a G value, which is beyond the range of a hexadecimal number.

AB.07.CF.62.16.BD MAC addresses are comprised of 12 hexadecimal digits (ranging from 0-9 and A-F). They are typically represented as a three sets of four hexadecimal digits or six sets of two hexadecimal digits separated with periods. Regardless of the grouping and separator values, look for 12 hex digits for a valid MAC address.

It is typically represented by hexadecimal numbers. It is a 48-bit address The MAC address identifies the physical address of the network adapter. The MAC address is a 12-digit (48-bit) hexadecimal number (each number ranges from 0-9 or A-F). The address is often written as 00-B0-D0-06-BC-AC OR 00B0.D006.BCAC, although dashes, periods, and colons can be used to divide the MAC address parts. An IPv4 address is 32-bits and uses octets of decimal numbers between 0-255. An IPv6 address is a 64-bit address that uses 32 hexadecimal numbers.

ARP Hosts use the Address Resolution Protocol (ARP) to discover the hardware address of a host.

Router A router is a device that links multiple networks and directs traffic between networks. Each network linked by routers has its own unique identifier called the "network number" or "network address."

Firewall The role of a firewall is to provide a barrier between an organization's network and a public network, such as the Internet. Its job is to prevent unauthorized access into the organization's private network. To do this, the firewall examines incoming packets and determines whether they should be allowed to enter based on a set of rules defined by the network administrator.

Firewall A firewall is the best device to deploy to protect your private network from a public untrusted network. Firewalls are used to control traffic entering and leaving your trusted network environment. Firewalls can manage traffic based on source or destination IP address, port number, service protocol, application or service type, user account, and even traffic content. Routers offer some packet-based access control, but not as extensive as that of a full-fledged firewall. Hubs and gateways are not sufficient for managing the interface between a trusted and an untrusted network.

To prevent hackers from accessing your network. Firewalls prevent unauthorized users from accessing private networks connected to the internet. You should never allow public access to your DHCP server. A proxy server caches web pages. A NAT router or ICS translates Web addresses to private IP addresses. A proxy server and NAT software might be implemented on the same device as your firewall, but they are different concepts.

Firewall A firewall allows you to filter unwanted traffic from the Internet to your network. Packet Internet Groper is better known by its acronym, PING, a TCP/IP command. A proxy server caches web pages. ICS allows you to connect a small network to the Internet through a single connection.