1 Chapter Overview Network devices

Hubs Broadcast For star topology Same as a repeater Operate at the physical layer 2

Modems Short for Modulator/Demodulator Digital to analog then to digital Phone (POTS – plain old telephone service) DSL (Digital Subscriber Line) Allow network signals to pass over phone lines Cable 3

Network Interface Card (NIC) Supports a protocol Convert parallel digitals signal to serial analog signal and serial analog signal to parallel digital signals Mostly built in now Has LEDs to show if the line is live and transmitting data Transceiver – converting signals from, say 100Base0TX to 100Base0FX 4

5 An (Old) Combination Ethernet NIC

6 A BNC Connector with a T Attached

7 An Ethernet NIC with an RJ-45 Jack

Bridge Connect similar network segment together Break collision domains Designed for the bus topology 8

Switch Point to point communication Segment the message in Switch-hub setting – function like a bridge Know MAC address 9

Wireless Access Point (AP) Support a/b/g/n 10

11 Understanding Routing A router is a system connected to two or more networks that forwards packets from one network to another. Routers operate at the network layer, sometimes referred as layer 3, of the Open Systems Interconnection (OSI) reference model. Routers can connect networks running different data- link layer protocols and different network media. Large internetworks often have redundant routers, providing multiple routes to a destination. Routers select the most efficient route to each destination.

12 Redundant Routers

13 Router Products The Microsoft Windows 2000~2012, Microsoft Windows NT, and Novell NetWare operating systems include routing capability. A stand-alone router is a hardware device that is essentially a special-purpose computer (with CPU, RAM, HD, and NICs). More in later chapters

Firewall Can be software or hardware It separates Intranet from Internet 14

15 DHCP Addresses the shortcomings of RARP and BOOTP (two other protocols) Dynamically allocates IP addresses from a pool Reclaims unused addresses Prevents IP address duplication

16 DHCP Address Allocation Types Manual allocation Static IP address, DHCP is only good for lookups Automatic allocation Same IP address, assigned by DHCP server Dynamic allocation (Next page)

17 Dynamic Allocation The DHCP server leases to the client an IP address chosen from a pool. The client must periodically renew the lease address. Unrenewed lease addresses are returned to the pool. Dynamic allocation allows you to add, remove, and relocate computers.

18 The IP Address Leasing Process The address assignment process is the same for all of the allocation methods. Clients using manual or automatic allocation receive no further communication after the address assignment. Clients using dynamic allocation lease IP addresses for a time interval specified by the server. The client must renew the lease on a regular basis to continue using it. DHCP address leases are typically measured in days. If addresses are in short supply, a shorter lease interval is warranted. If computers are rarely moved to other subnets, longer lease intervals reduce the DHCP traffic.

19 Others Multilayer Switch – level 3 switch Content Switch/Web Switch Operate at even higher level than 3 Rout to different web server based on requesting content Intrusion Detection or Prevention System Really? Firmware version of software Load Balancer DNS Server (Domain Name Service) Convert IP address to domain name back Proxy Server

Useful URL 20