Understanding Network Devices: Hubs, Routers, Firewalls, and DHCP Management

1. Chapter Overview • Network devices

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

3. 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

4. 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

5. An (Old) Combination Ethernet NIC

6. A BNC Connector with a T Attached

7. An Ethernet NIC with an RJ-45 Jack

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

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

10. Wireless Access Point (AP) • Support 802.11a/b/g/n

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

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

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

20. Useful URL • http://www.tcpipguide.com/free/