Ethernet Basics and Network Troubleshooting

1. Ethernet Basics and Network Troubleshooting Wires, switches, hubs, and what to plug where Title ScreenTitle Screen

2. Networking Communication between two or more devices. Parts required for Networking: Host Computer, networked printer, etc. Sends/receives data for network to card Card Every card on a network has to have a unique address Card breaks outgoing data into packets and addresses them Card receives packets addressed to it and re-assembles packets to data Wire Transmits packets across network For this discussion includes all wires, radios and devices between network cards (including hubs, switches, access points, etc.) Definition of networking, parts required to build a network.Definition of networking, parts required to build a network.

3. Wire types Co-Ax Composed of: Core, insulation, shielding, insulation 10 Mb only 10Base5 �Thicknet� 1600 ft (500 meters) 10Base2 �Thinnet� 600 ft (200 meters) Twisted Pair 10/100/1000 Mb 340 ft. (100 meters) between devices CAT3, CAT5, CAT5e, CAT6, CAT6e Co-Ax has a �core� wire surrounded by a insulated material, then a metal shielding, encased in a insulator. Twisted pair has 4 pairs of twisted wire, the twists in the wires help eliminate interference. UTP wires have shorter useable lengths but allows more flexible configurations.Co-Ax has a �core� wire surrounded by a insulated material, then a metal shielding, encased in a insulator. Twisted pair has 4 pairs of twisted wire, the twists in the wires help eliminate interference. UTP wires have shorter useable lengths but allows more flexible configurations.

4. Wire Types (cont.) Fiber 10/100/1000/10,000 Mb Multi-mode � Long Haul (20 km) Single-mode � �Short Haul� (3 Km) what we use Carries light, not electricity Wireless Speeds 11/7 Mb, 54/27Mb Because of encryption and connection upkeep, available bandwidth is about � of stated speed Common �mediums� InfraRed (IR) Microwave, (long distances) Radio Licensed/private Un-licensed (802.11b/g/a) Fiber optic cable uses clear plastic or glass fibers to carry light. Multi-mode fiber has a core of more dense material surrounded by a less dense material the bends the light back into the core, this allows the fiber to carry a signal to greater distances. (up to 20 Km) Singe-mode fiber consists of a solid simple, core. Costs less shorter distance limitation (3 Km or less.) Wireless is less reliable, and slower than wired technologies, used where wires are too expensive to use, or where convenience and flexibility are more important than speed.Fiber optic cable uses clear plastic or glass fibers to carry light. Multi-mode fiber has a core of more dense material surrounded by a less dense material the bends the light back into the core, this allows the fiber to carry a signal to greater distances. (up to 20 Km) Singe-mode fiber consists of a solid simple, core. Costs less shorter distance limitation (3 Km or less.) Wireless is less reliable, and slower than wired technologies, used where wires are too expensive to use, or where convenience and flexibility are more important than speed.

5. Ethernet (Infancy) 10Base5 � �Original Ethernet� Large Co-ax Backbone (garden hose) Terminated at ends Vampire tap, to transceiver 1600 ft. backbone �Jumper� from transceiver to card How it works: 10 Mb/s One Wire� every packet goes to every host CSMA/CD (Carrier Sense Multiple Access/ Carrier Detect) Collisions Half Duplex Original Ethernet on large Co-Ax cable, one wire, bandwidth shared with all hosts. CSMA/CD there are collisions. All communication is half duplex, like a CB radio, can�t talk and listen at the same time.Original Ethernet on large Co-Ax cable, one wire, bandwidth shared with all hosts. CSMA/CD there are collisions. All communication is half duplex, like a CB radio, can�t talk and listen at the same time.

6. Ethernet (Toddler) 10Base2 Smaller diameter, less expensive cable shorter length 600 ft total length Get rid of the �backbone� use a �T� connector on each card Daisy chained the whole network together Terminated on ends Still ONE WIRE Still CSMA/CD Cutting cost by using smaller diameter cable and �T� connectors, resulted in a shorter network (1000 ft shorter) but a less reliable one. If there is an open �T� connector, or any un-plugged connection it would not work.Cutting cost by using smaller diameter cable and �T� connectors, resulted in a shorter network (1000 ft shorter) but a less reliable one. If there is an open �T� connector, or any un-plugged connection it would not work.

7. Ethernet (Adolescent) 10BaseT HUB Packet is simultaneously sent out all ports If two packets come in at the same time it is a collision Twisted pair wire The Hub is part of �The Wire� 340 feet between devices 3 hops maximum (no daisy chaining) Changing to a �Star� topology made for a more flexable and changeable network. Lower costing than the expensive 10Base5 �thicknet� more, expensive than �thinnet� No more termination or wire disconnects �breaking� the network. Data that goes through more than 3 hubs becomes corrupt, still works but slower. Still �one wire� all data goes simultaneously out all ports. Changing to a �Star� topology made for a more flexable and changeable network. Lower costing than the expensive 10Base5 �thicknet� more, expensive than �thinnet� No more termination or wire disconnects �breaking� the network. Data that goes through more than 3 hubs becomes corrupt, still works but slower. Still �one wire� all data goes simultaneously out all ports.

8. Limitations/Issues Still CSMA/CD Hubs �listen� (receive) on the transmit wires, �send� (transmit) on the receive wires (backwards to a host) Connections between hubs need to be �crossed over� Crossover cable (red) MIDX switch MIDX port Auto Negotiate on one end (or both) Speeds Early years 10 Mb/s - 70 stations, average network traffic 50% of packets are collisions, �useable� bandwidth 5 Mb/s Later 100 Mb/s - faster data rate, faster collisions, 7 stations, average network traffic, 50% of all packets are collisions, useable bandwidth 50 Mb/s Last class of hub, 10/100 �dual speed� hub Has a two �sides�, auto detects host�s speed If 10 Mb/s, puts on 10 Mb/s side of switch If 100 Mb/s, puts on 100 Mb side of switch

9. Where we were 10 yrs ago & theLimitations: �One Wire� All data goes to every Host Total bandwidth shared by ALL hosts Relied on CSMA/CD Collisions � if / when two hosts �talk� at the same time, both stop, wait a random period of time and try again (70 computers on 10BaseT average 50% collisions) Half Duplex ONLY, like a CB radio 3 HOP rule If packets go through more than 3 hubs, it may become corrupt Corrupt packets are re-requested and must be re-sent Using co-ax and hubs we had a lot of limitations, issues, and rules to live with.Using co-ax and hubs we had a lot of limitations, issues, and rules to live with.

10. SWITCHES!!!! Switches are INTELEGENT: Have CPU & RAM Builds a table, what address is on what port Switches can do Full Duplex. Store and Forward Packet comes into switch, is looked at and sent out only on the port(s) that it needs to go to No �3 hop� rule Switches are �SMART�, they are simple computers. Build a table and �manage� traffic. Devices plugged into switches can do Full Duplex, talk and listen at the same time. Because switches use store, analyze, and forward. They �fix� many problems: No three hop rule�Switches are �SMART�, they are simple computers. Build a table and �manage� traffic. Devices plugged into switches can do Full Duplex, talk and listen at the same time. Because switches use store, analyze, and forward. They �fix� many problems: No three hop rule�

11. SWITCHES!!! (Cont.) Switches can handle multiple speeds. This allows multiple 10/100 workstations to talk full speed to a 1000 Mb/sec server connection Reduces/Eliminates Collisions Dedicated bandwidth to each port in switch �Big� switches are �managed�, has an IP address and you can customize ports Switches can send different packets to different ports simultaneously, even at different speeds. Principle on elimination of collisions, each port is a �Collision Domain� collisions are not replicated between switched ports. Each device plugged into a switch has a dedicated full bandwidth connection to the switch. Big or �Core� switches can be configured on a port to port basis.Switches can send different packets to different ports simultaneously, even at different speeds. Principle on elimination of collisions, each port is a �Collision Domain� collisions are not replicated between switched ports. Each device plugged into a switch has a dedicated full bandwidth connection to the switch. Big or �Core� switches can be configured on a port to port basis.

12. Switches, limitations Traffic that still goes to every port: Broadcast traffic (addressed to 255.255.255.255) Multicast Traffic (Imaging) �Smart� switches pay attention and only send the multicast traffic to the clients once they have responded Lower end switches, any packet not on the table goes to all ports (the response from the unknown host will add it to the table) If a switch overruns it�s table (runs out of ram) it goes into �blocking� mode, basically becomes a hub Still may need to use crossover cable, MIDX port, some switches �auto negotiate� crossover There are still limitations even with switches. Some types of traffic still have to go to every port, Broadcast and Multicast packets. Packets addressed to devices not on the switches table are sent out all ports, hopefully the reply back from the device will get it added to the tables. Low end switches may be too low in RAM to work on our networks, may go into �blocking mode� if can�t handle our networks. There are still limitations even with switches. Some types of traffic still have to go to every port, Broadcast and Multicast packets. Packets addressed to devices not on the switches table are sent out all ports, hopefully the reply back from the device will get it added to the tables. Low end switches may be too low in RAM to work on our networks, may go into �blocking mode� if can�t handle our networks.

13. GIGABIT Ethernet Eliminated CSMA/CD There is no such thing as a Gigabit hub, it�s switched only! NO Collisions (it can�t detect them or correct them, so they simply aren�t allowed) Copper Gig Uses all 8 wires, each one individually Requires CAT5e or better CAT5e keep under 250 feet (prefer CAT6) All copper gig equipment auto-negotiates crossover/duplex/speed No Crossover cable needed, if used must have all 4 pairs crossed over Gigabit and faster Ethernet protocols would no work with CSMA/CD, packets come in too fast to detect collisions. This means that every connection is switched, there is no hubs at this speed. The �wire type� has nothing to do with speed. Copper gig is the same speed as fiber gig. Coper gig is a strange beast, uses every wire differently, in each pair one wire transmits the other receives. EVERY copper gig connection is crossed over in the switch/card. No crossover cable needed. If you do use a crossover cable, be sure that all 4 pairs are wired to crossover, otherwise it will go to 100 Mb, using 2 pairs only.Gigabit and faster Ethernet protocols would no work with CSMA/CD, packets come in too fast to detect collisions. This means that every connection is switched, there is no hubs at this speed. The �wire type� has nothing to do with speed. Copper gig is the same speed as fiber gig. Coper gig is a strange beast, uses every wire differently, in each pair one wire transmits the other receives. EVERY copper gig connection is crossed over in the switch/card. No crossover cable needed. If you do use a crossover cable, be sure that all 4 pairs are wired to crossover, otherwise it will go to 100 Mb, using 2 pairs only.

14. Wireless 50% of the bandwidth used for encryption, connection and error correction 11 Mb 802.11b �useable� bandwidth is 7 Mb 54 MB 802.11a/g �useable� bandwidth is 24 Mb 802.11n, uses more channels (less access points pre area more contention for channels) Faster, more reliable A wireless access point is a HUB All communication between the wireless hosts and the access point are on one radio channel (wire). All hub limitations apply Wireless is slower than wired for two reasons: First, 40% of the bandwidth is used for the larger packet headers and special packets used to maintain the connection. Wireless communications work as a hub. All the devices communicate on the same �wire� or channel.Wireless is slower than wired for two reasons: First, 40% of the bandwidth is used for the larger packet headers and special packets used to maintain the connection. Wireless communications work as a hub. All the devices communicate on the same �wire� or channel.

15. Summary so far Hubs Stink!!! Half Duplex only Collisions are the norm Shared bandwidth between all devices on hubs Wireless is slower than wired It�s a hub, and 40% of bandwidth is wasted But, it�s darned convenient (that�s why we use it) If you can use a wired connection, do so Try and keep it to 15 or fewer computers per access point Use switches Full duplex Eliminates Collisions Dedicated bandwidth to each switched port 3-20 times faster than hubs Hubs are slower, half duplex, collisions, and shared bandwidth (one wire) Wireless is slower than wired Switches solve a majority of the problems with Ethernet in a hub based environment. Hubs are slower, half duplex, collisions, and shared bandwidth (one wire) Wireless is slower than wired Switches solve a majority of the problems with Ethernet in a hub based environment.

16. Ethernet Troubleshooting What does �network does not work� mean? Internet down Server down One computer, or group of computers can�t access network Wing of building down Whole building down Understand the �path� data takes through the network What does work, and specifically, what does not The first part of troubleshooting is to understand where/what the problem is. First figure out what IS working, and what is not.The first part of troubleshooting is to understand where/what the problem is. First figure out what IS working, and what is not.

17. Common problems Four common network problem categories: Everything is slow/not working Internet is slow, server access is normal Server access is slow/not working, Internet access seems normal Single computer, room of computers, area of building is slow/not working

19. Everything is slow/not working Wiring/Network problems Ethernet loops (nasty to find, messes up whole school) Two wires to wall? (use ONE red cable) Use a red cable to the wall. Count cables/computers Remove extra cables (teachers/kids love to plug stuff in) Airport extreme, both wires to wall

22. Everything is slow/not working (cont.) Wiring/Network problems (cont.) Cable too long (less than 320� from switch to host) Cable with electrical/florescent ballast? Hubs still there? Daisy chained hubs (deeper than 3?)

23. Everything is slow/not working (cont.) Network is very busy, so it�s slow (solid activity lights on switches) Look at lights on MDF/IDF switches, unplug-replug one at a time to see if traffic returns to normal - note the port and track it down Causes: Worm viruses/spyware Loop �Chattery Network Card� (bad drivers or bad card) Keep OS updates and anti-Virus software up to date Have NE analyze network

24. Internet is slow/not working (cont.) Can be a Router Problem Contact your NE/Helpdesk then Turn router off and back on Can be a �Upstream� problem Ping around

25. Internet is slow/not working Overloaded Wan line(s) Can be worm/e-mail viruses eating up bandwidth Can be peer-to-peer file sharing program on a computer in your school Streaming video/audio congesting the network? (video/audio over the internet is for educational use only, not for entertainment)

26. Ping around Get to a command prompt XP/Win2k/Vista Run �ipconfig� Note your default gateway Run �Ping <default gateway>� No response, your router may not be working Run �Ping <known district server/router> No response, your connection to the outside world (Geomax/T1 etc) is down Run �ping www.xmission.com� No response - your district�s connection to the outside world is down

27. Server is slow/not working Work this with your NE!! What you *CAN* do Step 1 Un-plug/re-plug the server�s network cables First Contact helpdesk/your NE. Don�t move them, plug them back in the same place Only do one end of one cable at a time The server will be �down� while they are un-plugged Step 2 (still not working) Check it out, or have the network guy check it out Contact helpdesk/your NE, get server restarted

28. Group of computers is slow/not working What do they have in common? All connected to same hub? Get a switch!!! All connected to same mini-switch? Power-cycle switch Check for loops Replace switch ($18.00 for 8 port.) Change port on IDF/MDF

29. Group of computers is slow/not working (cont.) What do they have in common? (cont.) All same model/from same image? Virus/Spyware in image? Client software installed/configured wrong? OS not patched? Bad NIC driver? Same �wing� or area Power cycle switches in IDF/MDF (some of these take over 3 min. to boot, so don�t just go and do this without warning users)

30. Single computer is slow/not working Restart the computer Un-plug/re-plug/replace cables Check it�s connection at MDF/IDF

31. Single computer is slow/not working (cont.) Change it�s port at MDF/IDF Don�t move other wires Don�t �clean up� wiring!!! If it doesn't fix it, change it back Patches/ AntiVirus / Spyware Upgrade/Re-install NIC driver Replace NIC Force speed/duplex (gig switch, Cat5 wiring?)