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6 network devices

The document discusses various networking devices and their functions. Repeaters work at the physical layer to regenerate signals and extend the distance of a network by combating attenuation. Bridges operate at the data link layer, segmenting networks and reducing traffic by only forwarding frames to relevant segments based on MAC addresses. Switches improve performance over bridges by opening virtual circuits between communicating devices to avoid contention. Routers connect multiple network segments and operate at the network layer, using logical IP addresses to route packets. Gateways have the most negative impact on performance as they must fully translate between different protocol suites.

Tecnología◦Educación◦
NETWORK DEVICES LECTURE 6
REPEATERS • THE NUMBER OF NODES ON A NETWORK AND THE LENGTH OF CABLE USED • INFLUENCE THE QUALITY OF COMMUNICATION ON THE NETWORK • ATTENUATION • THE DEGRADATION OF SIGNAL CLARITY • REPEATERS • WORK AGAINST ATTENUATION BY REPEATING SIGNALS THAT THEY RECEIVE ON A NETWORK • TYPICALLY CLEANING AND REGENERATING THE DIGITAL TRANSMISSION IN THE PROCESS 2 CCNA Guide to Cisco Networking Fundamentals
REPEATERS (CONTINUED) 3 CCNA Guide to Cisco Networking Fundamentals
REPEATERS (CONTINUED) • NOTE THAT ON ANALOG NETWORKS, DEVICES THAT BOOST THE SIGNAL ARE CALLED AMPLIFIERS • THESE DEVICES DO NOT HAVE THE SAME SIGNAL REGENERATION CAPABILITIES AS REPEATERS • BECAUSE THEY MUST MAINTAIN THE SHAPE OF THE RECEIVED SIGNAL • REPEATERS WORK IN THE PHYSICAL LAYER (LAYER 1) • ON OPTICAL NETWORKS, SIGNAL AMPLIFICATION IS HANDLED BY OPTICAL REPEATERS 4 • SOME REPEATERS CAN BE USED TO CONNECT TWO PHYSICALLY DIFFERENT TYPES OF CABLING CCNA Guide to Cisco Networking Fundamentals
REPEATERS (CONTINUED) 5 CCNA Guide to Cisco Networking Fundamentals
HUBS • HUB • GENERIC CONNECTION DEVICE USED TO TIE SEVERAL NETWORKING CABLES TOGETHER TO CREATE A LINK BETWEEN DIFFERENT STATIONS ON A NETWORK • ACTIVE HUBS • AMPLIFY OR REPEAT SIGNALS THAT PASS THROUGH THEM • PASSIVE HUB • MERELY CONNECTS CABLES ON A NETWORK AND PROVIDES NO SIGNAL REGENERATION 6 • TOPOLOGY REFERS TO THE PHYSICAL LAYOUT OF NETWORK CABLE AND DEVICES CCNA Guide to Cisco Networking Fundamentals
HUBS (CONTINUED) 7 CCNA Guide to Cisco Networking Fundamentals
ADVANTAGES OF REPEATERS AND HUBS • ADVANTAGES • CAN EXTEND A NETWORK’S TOTAL DISTANCE • DO NOT SERIOUSLY AFFECT NETWORK PERFORMANCE • CERTAIN REPEATERS CAN CONNECT NETWORKS USING DIFFERENT PHYSICAL MEDIA 8 CCNA Guide to Cisco Networking Fundamentals
DISADVANTAGES OF REPEATERS AND HUBS (CONTINUED) • DISADVANTAGES • CANNOT CONNECT DIFFERENT NETWORK ARCHITECTURES, SUCH AS TOKEN RING AND ETHERNET • DO NOT REDUCE NETWORK TRAFFIC • THEY REPEAT EVERYTHING THEY RECEIVE • DO NOT SEGMENT THE NETWORK • DO NOT REFORMAT DATA STRUCTURES • CANNOT CONNECT NETWORKS THAT REQUIRE DIFFERENT TYPES OF FRAMES • REPEATERS DO NOT SEGMENT A NETWORK 9 • FRAMES THAT ARE BROADCAST ON A GIVEN SEGMENT MAY CCNA Guide to Cisco Networking COLLIDE Fundamentals • DEVICES THAT “SEE” THE TRAFFIC OF OTHER DEVICES ARE
NETWORK SEGMENTATION • SEGMENTATION • THE BREAKING DOWN OF A SINGLE HEAVILY POPULATED NETWORK SEGMENT INTO SMALLER SEGMENTS, OR COLLISION DOMAINS, POPULATED BY FEWER NODES • SEGMENT • PART OF A NETWORK THAT IS DIVIDED LOGICALLY OR PHYSICALLY FROM THE REST OF THE NETWORK • WHEN NETWORK ADMINISTRATORS PLACE TOO MANY NODES ON THE SAME NETWORK SEGMENT • CAUSES THE NUMBER OF COLLISIONS TO INCREASE 10 CCNA Guide to Cisco Networking Fundamentals
11 CCNA Guide to Cisco Networking Fundamentals
BRIDGES • BRIDGES • OPERATE AT THE DATA LINK LAYER OF THE OSI MODEL • FILTER TRAFFIC BETWEEN NETWORK SEGMENTS BY EXAMINING THE DESTINATION MAC ADDRESS • BASED ON THE DESTINATION MAC ADDRESS, THE BRIDGE EITHER FORWARDS OR DISCARDS THE FRAME • REDUCE NETWORK TRAFFIC BY KEEPING LOCAL TRAFFIC ON THE LOCAL SEGMENT • BROADCAST FRAME • FRAME DESTINED FOR ALL COMPUTERS ON THE NETWORK 12 CCNA Guide to Cisco Networking Fundamentals
13 CCNA Guide to Cisco Networking Fundamentals
TRANSPARENT BRIDGES • ALSO CALLED LEARNING BRIDGES • BECAUSE THEY BUILD A TABLE OF MAC ADDRESSES AS THEY RECEIVE FRAMES • THEY “LEARN” WHICH ADDRESSES ARE ON WHICH SEGMENTS • THE BRIDGE USES THE SOURCE MAC ADDRESSES TO DETERMINE WHICH ADDRESSES ARE ON WHICH SEGMENTS • BY DETERMINING A FRAME’S ORIGIN, THE BRIDGE KNOWS WHERE TO SEND FRAMES IN THE FUTURE • ETHERNET NETWORKS MAINLY USE TRANSPARENT BRIDGES 14 CCNA Guide to Cisco Networking Fundamentals
SOURCE-ROUTING BRIDGES • RELY ON THE SOURCE OF THE FRAME TRANSMISSION TO PROVIDE THE ROUTING INFORMATION • THE SOURCE COMPUTER DETERMINES THE BEST PATH BY SENDING OUT EXPLORER FRAMES • THE SOURCE INCLUDES THE ROUTING INFORMATION RETURNED BY ITS EXPLORER FRAMES IN THE FRAME SENT ACROSS THE NETWORK • THE BRIDGE USES THIS INFORMATION TO BUILD ITS TABLE 15 CCNA Guide to Cisco Networking Fundamentals
TRANSLATION BRIDGES • CAN CONNECT NETWORKS WITH DIFFERENT ARCHITECTURES, SUCH AS ETHERNET AND TOKEN RING • THESE BRIDGES APPEAR AS: • TRANSPARENT BRIDGES TO AN ETHERNET HOST • SOURCE-ROUTING BRIDGES TO A TOKEN RING HOST 16 CCNA Guide to Cisco Networking Fundamentals
ADVANTAGES OF BRIDGES • ADVANTAGES • CAN EXTEND A NETWORK BY ACTING AS A REPEATER • CAN REDUCE NETWORK TRAFFIC ON A SEGMENT BY SUBDIVIDING NETWORK COMMUNICATIONS • INCREASE THE AVAILABLE BANDWIDTH TO INDIVIDUAL NODES BECAUSE FEWER NODES SHARE A COLLISION DOMAIN • REDUCE COLLISIONS • SOME BRIDGES CONNECT NETWORKS USING DIFFERENT MEDIA TYPES AND ARCHITECTURES 17 CCNA Guide to Cisco Networking Fundamentals
DISADVANTAGES OF BRIDGES • DISADVANTAGES • SLOWER THAN REPEATERS AND HUBS • EXTRA PROCESSING BY VIEWING MAC ADDRESSES • FORWARD BROADCAST FRAMES INDISCRIMINATELY, SO THEY DO NOT FILTER BROADCAST TRAFFIC • MORE EXPENSIVE THAN REPEATERS AND HUBS • BROADCAST STORM • WHEN TWO OR MORE STATIONS ENGAGE IN THE TRANSMISSION OF EXCESSIVE BROADCAST TRAFFIC 18 CCNA Guide to Cisco Networking Fundamentals
SWITCHES • SWITCHES • OPERATE AT THE DATA LINK LAYER OF THE OSI MODEL • INCREASE NETWORK PERFORMANCE BY REDUCING THE NUMBER OF FRAMES TRANSMITTED TO THE REST OF THE NETWORK • SWITCH OPENS A VIRTUAL CIRCUIT BETWEEN THE SOURCE AND THE DESTINATION • PREVENTS COMMUNICATIONS BETWEEN JUST TWO COMPUTERS FROM BEING BROADCAST TO EVERY COMPUTER ON THE NETWORK OR SEGMENT • CALLED MICROSEGMENTATION 19 CCNA Guide to Cisco Networking Fundamentals
SWITCHES (CONTINUED) • WHEN TWO MACHINES HAVE A VIRTUAL CIRCUIT • THEY DO NOT HAVE TO SHARE THE BANDWIDTH WITH ANY OTHER COMPUTERS • MULTIPLE VIRTUAL CIRCUITS CAN BE IN USE AT THE SAME TIME, EACH WITH ITS OWN FULL BANDWIDTH • CALLED “SWITCHED BANDWIDTH” • WHEN MACHINES MUST SHARE A WIRE AND COMPETE FOR AVAILABLE BANDWIDTH WITH OTHER MACHINES, THEY EXPERIENCE CONTENTION 20 CCNA Guide to Cisco Networking Fundamentals
21 CCNA Guide to Cisco Networking Fundamentals
ADVANTAGES OF SWITCHES • ADVANTAGES • SWITCHES INCREASE AVAILABLE NETWORK BANDWIDTH • SWITCHES REDUCE THE WORKLOAD ON INDIVIDUAL COMPUTERS • SWITCHES INCREASE NETWORK PERFORMANCE • NETWORKS THAT INCLUDE SWITCHES EXPERIENCE FEWER FRAME COLLISIONS BECAUSE SWITCHES CREATE COLLISION DOMAINS FOR EACH CONNECTION (A PROCESS CALLED MICROSEGMENTATION) • SWITCHES CONNECT DIRECTLY TO WORKSTATIONS 22 CCNA Guide to Cisco Networking Fundamentals
DISADVANTAGES OF SWITCHES • DISADVANTAGES • SWITCHES ARE SIGNIFICANTLY MORE EXPENSIVE THAN BRIDGES • NETWORK CONNECTIVITY PROBLEMS CAN BE DIFFICULT TO TRACE THROUGH A SWITCH • BROADCAST TRAFFIC MAY BE TROUBLESOME 23 CCNA Guide to Cisco Networking Fundamentals
ROUTERS • ROUTERS • OPERATE AT THE NETWORK LAYER OF THE OSI MODEL • PROVIDE FILTERING AND NETWORK TRAFFIC CONTROL ON LANS AND WANS • CAN CONNECT MULTIPLE SEGMENTS AND MULTIPLE NETWORKS • INTERNETWORKS • NETWORKS CONNECTED BY MULTIPLE ROUTERS • SIMILAR TO SWITCHES AND BRIDGES IN THAT THEY SEGMENT A NETWORK AND FILTER TRAFFIC • ROUTERS USE THE LOGICAL ADDRESS 24 CCNA Guide to Cisco Networking Fundamentals
PHYSICAL VS. LOGICAL ADDRESSES • MAC ADDRESS • FOUND AT THE DATA LINK LAYER OF THE OSI MODEL • USED BY BRIDGES AND SWITCHES TO MAKE FORWARDING DECISIONS WITHIN A NETWORK OR SUBNETWORK • IP ADDRESS • LOGICAL ADDRESS WHEN TCP/IP IS USED ON AN INTERNETWORK • ROUTERS USE THE IP ADDRESS TO ROUTE PACKETS TO THE CORRECT NETWORK SEGMENT 25 CCNA Guide to Cisco Networking Fundamentals
PHYSICAL VS. LOGICAL ADDRESSES (CONTINUED) 26 CCNA Guide to Cisco Networking Fundamentals
ADVANTAGES OF ROUTERS • ADVANTAGES • CAN CONNECT DIFFERENT NETWORK ARCHITECTURES, SUCH AS ETHERNET AND TOKEN RING • CAN CHOOSE THE BEST PATH ACROSS AN INTERNETWORK USING DYNAMIC ROUTING TECHNIQUES • REDUCE NETWORK TRAFFIC BY CREATING COLLISION DOMAINS • REDUCE NETWORK TRAFFIC BY CREATING BROADCAST DOMAINS 27 CCNA Guide to Cisco Networking Fundamentals
DISADVANTAGES OF ROUTERS • DISADVANTAGES • ROUTERS WORK ONLY WITH ROUTABLE NETWORK PROTOCOLS; MOST BUT NOT ALL PROTOCOLS ARE ROUTABLE • ROUTERS ARE MORE EXPENSIVE THAN OTHER DEVICES • DYNAMIC ROUTER COMMUNICATIONS (INTER-ROUTER COMMUNICATION) CAUSE ADDITIONAL NETWORK OVERHEAD, WHICH RESULTS IN LESS BANDWIDTH FOR USER DATA • ROUTERS ARE SLOWER THAN OTHER DEVICES BECAUSE THEY MUST ANALYZE A DATA TRANSMISSION FROM THE PHYSICAL THROUGH THE NETWORK LAYER 28 CCNA Guide to Cisco Networking Fundamentals
29 CCNA Guide to Cisco Networking Fundamentals
GATEWAYS • GATEWAY • USUALLY A COMBINATION OF HARDWARE AND SOFTWARE • TRANSLATES BETWEEN DIFFERENT PROTOCOL SUITES • HAS THE MOST NEGATIVE EFFECT ON NETWORK PERFORMANCE • PACKETS MUST BE REBUILT NOT JUST AT THE LOWER LEVELS BUT AT THE VERY UPPER LEVELS • SO THAT ACTUAL DATA CONTENT CAN BE CONVERTED INTO A FORMAT THE DESTINATION CAN PROCESS • CREATES THE MOST LATENCY 30 CCNA Guide to Cisco Networking Fundamentals